Class 11 Economics Chapter 12 — Production and Costs (English Medium, ASSEB)
Welcome to HSLC Guru! This English-medium study guide for ASSEB Class 11 Economics, Chapter 12 — Production and Costs presents a thorough summary, complete textbook question and answers (1-mark, 2–3 mark, and 5–6 mark), additional MCQs, fill-in-the-blanks, true/false items, a glossary, and a quick formula table. Whether you are revising before an exam or learning the topic for the first time, this article will help you master the production function, the law of variable proportions, returns to scale, and the family of cost concepts and curves used in the theory of the firm.
Summary of the Chapter
Production function and time periods. Production is the process of transforming inputs (factors of production such as land, labour, capital, and entrepreneurship) into outputs (goods and services). The technical relationship between physical inputs and the maximum output that can be obtained from them, given the state of technology, is called the production function. It is generally written as Q = f(L, K), where Q is output, L is labour, and K is capital. Economists distinguish between two time periods. The short run is a period in which at least one factor (usually capital) is fixed while others (usually labour) can be varied. The long run is a period long enough for the firm to vary all its inputs; there are no fixed factors in the long run. This distinction is fundamental because the laws governing returns to a factor (short run) differ from those governing returns to scale (long run).
Total, Average and Marginal Product. When only one variable input (say labour) is changed and other inputs are held constant, three product concepts emerge. Total Product (TP) is the total quantity of output produced by employing a given amount of the variable input. Average Product (AP) is the output per unit of the variable input, that is AP = TP / L. Marginal Product (MP) is the addition to TP when one more unit of the variable input is employed: MPn = TPn − TPn−1. The relationship between AP and MP is precise: when MP > AP, AP rises; when MP = AP, AP is at its maximum; and when MP < AP, AP falls. Behind these patterns lies the celebrated Law of Variable Proportions, which states that as more and more units of a variable input are combined with fixed inputs, TP first increases at an increasing rate, then at a diminishing rate, and finally falls. Accordingly the law identifies three stages: Stage I (increasing returns to a factor), Stage II (diminishing returns to a factor) and Stage III (negative returns). A rational producer always operates in Stage II, where MP is positive but falling and AP is also falling.
Returns to Scale. In the long run, when all inputs are varied in the same proportion, the change in output describes returns to scale. If output rises by a larger proportion than the inputs, the firm enjoys increasing returns to scale (IRS). If output rises in the same proportion as inputs, there are constant returns to scale (CRS). If output rises by a smaller proportion than inputs, the firm faces decreasing returns to scale (DRS). IRS arises from indivisibilities, specialisation, and economies of large scale; DRS arises mainly from managerial diseconomies. The shape of the long-run average cost (LAC) curve directly reflects these three phases of returns to scale.
Cost concepts and cost curves. In the short run, the firm faces fixed and variable costs. Total Fixed Cost (TFC) does not change with output; Total Variable Cost (TVC) changes with output; Total Cost (TC) = TFC + TVC. From these we derive average concepts: AFC = TFC/Q (a rectangular hyperbola, falling continuously), AVC = TVC/Q (U-shaped), and ATC = TC/Q = AFC + AVC (also U-shaped). Marginal Cost (MC) = ΔTC/ΔQ = ΔTVC/ΔQ is U-shaped and cuts both AVC and ATC at their respective minimum points from below. In the long run, with all factors variable, LAC is the envelope of short-run average cost curves and is also U-shaped, reflecting IRS, CRS and DRS. LMC intersects LAC at its minimum point. The AC–MC relationship is symmetrical to the AP–MP relationship: when MC < AC, AC falls; MC = AC at minimum AC; when MC > AC, AC rises.
Textbook Questions and Answers
A. 1-Mark Questions
Q1. Define production function.
Answer: The production function is the technical relationship between physical inputs and the maximum output of a good obtainable from them, given the state of technology. Symbolically, Q = f(L, K).
Q2. What is meant by short run?
Answer: Short run is the time period during which at least one factor of production (usually capital) remains fixed while other factors can be varied to change the level of output.
Q3. Define total product.
Answer: Total Product (TP) is the total quantity of output produced by a firm by employing a given amount of the variable input, with the fixed input held constant.
Q4. Write the formula for average product.
Answer: Average Product (AP) = Total Product (TP) ÷ Units of Variable Input (L).
Q5. Define marginal product.
Answer: Marginal Product (MP) is the addition to total product when one additional unit of the variable input is employed. MPn = TPn − TPn−1.
Q6. What is total fixed cost?
Answer: Total Fixed Cost (TFC) is the cost incurred by a firm on fixed factors of production. It remains the same at all levels of output, including zero output.
Q7. Define marginal cost.
Answer: Marginal Cost (MC) is the addition to total cost from producing one extra unit of output. MC = ΔTC/ΔQ = ΔTVC/ΔQ.
Q8. What is the shape of AFC curve?
Answer: The Average Fixed Cost (AFC) curve is downward sloping throughout and takes the shape of a rectangular hyperbola, since TFC is constant and AFC = TFC/Q falls as Q rises.
Q9. State the relation between AC and MC at minimum point of AC.
Answer: At the minimum point of the AC curve, AC = MC. The MC curve cuts the AC curve from below at this point.
Q10. Define returns to scale.
Answer: Returns to scale refers to the change in output when all inputs are varied simultaneously in the same proportion in the long run.
B. 2 / 3-Mark Questions
Q1. Distinguish between short run and long run.
Answer: (i) In the short run at least one factor (usually capital) is fixed, whereas in the long run all factors are variable. (ii) Short-run output adjustments take place by changing only the variable factor; long-run adjustments occur by changing scale of operation. (iii) The Law of Variable Proportions operates in the short run; the Law of Returns to Scale operates in the long run.
Q2. Explain the relationship between AP and MP.
Answer: The relationship between Average Product (AP) and Marginal Product (MP) is as follows: (i) When MP > AP, AP rises. (ii) When MP = AP, AP reaches its maximum. (iii) When MP < AP, AP falls. The MP curve cuts the AP curve from above at the highest point of AP. MP can become zero or even negative, but AP can never be negative as long as TP is positive.
Q3. Distinguish between fixed cost and variable cost.
Answer: Fixed costs are costs of fixed factors and remain unchanged at all levels of output (e.g., rent of factory, salary of permanent staff). They exist even when output is zero. Variable costs are costs of variable factors and change with the level of output (e.g., wages of casual labour, cost of raw materials). They are zero when output is zero.
Q4. Why is the AVC curve U-shaped?
Answer: AVC = TVC/Q. In the early stages of production, the variable factor is used more efficiently with the fixed factor, so AVC falls due to increasing returns to the variable factor. After the optimum point, diminishing returns set in and AVC begins to rise. Hence the curve falls, reaches a minimum and then rises, giving it a U-shape.
Q5. State three causes of increasing returns to scale.
Answer: (i) Indivisibility of factors: Some inputs (machinery, managers) are available only in lump sums and become more productive when fully utilised. (ii) Specialisation and division of labour: A larger scale allows workers to specialise, raising productivity. (iii) Internal and external economies: Bulk purchase, marketing, financial and risk-bearing economies lower per-unit cost as scale expands.
Q6. Show that TC = TFC + TVC and ATC = AFC + AVC.
Answer: Total cost is the sum of all costs of fixed and variable factors used to produce a given output, hence TC = TFC + TVC. Dividing both sides by output Q gives TC/Q = TFC/Q + TVC/Q, that is ATC = AFC + AVC. The vertical distance between ATC and AVC at any output is therefore equal to AFC and goes on diminishing as output rises.
C. 5 / 6-Mark Questions
Q1. Explain the Law of Variable Proportions with the help of a schedule.
Answer: The Law of Variable Proportions states that, as more and more units of a variable input are combined with a fixed input, total product first increases at an increasing rate, then at a diminishing rate, and finally falls. There are three stages of production:
Stage I — Increasing Returns: TP increases at an increasing rate, MP rises and reaches maximum, AP also rises. This is due to better utilisation of fixed factors and division of labour.
Stage II — Diminishing Returns: TP increases at a diminishing rate and reaches its maximum at the end. Both MP and AP fall, but MP remains positive. This stage ends when MP = 0. A rational producer operates in this stage.
Stage III — Negative Returns: TP starts falling, MP becomes negative. The variable factor has become so abundant relative to the fixed factor that it interferes with production. No firm operates in this stage.
The following hypothetical schedule (with capital fixed) illustrates these three stages:
| Units of Labour (L) | Total Product (TP) | Average Product (AP = TP/L) | Marginal Product (MP) | Stage |
|---|---|---|---|---|
| 1 | 10 | 10 | 10 | I |
| 2 | 24 | 12 | 14 | I |
| 3 | 39 | 13 | 15 | I (MP max) |
| 4 | 52 | 13 | 13 | I→II (AP max, AP=MP) |
| 5 | 60 | 12 | 8 | II |
| 6 | 66 | 11 | 6 | II |
| 7 | 66 | 9.43 | 0 | End of II (TP max) |
| 8 | 62 | 7.75 | −4 | III (negative MP) |
The schedule shows TP rising at an increasing rate up to the 3rd unit of labour, then increasing at a decreasing rate till the 7th unit (where TP is maximum and MP = 0), and finally falling thereafter (MP becomes negative). AP rises till L = 4 (where AP = MP = 13) and falls thereafter. This is the empirical content of the Law of Variable Proportions.
Q2. Explain the three phases of returns to scale with diagrams (description).
Answer: Returns to scale studies the response of output when all inputs are varied in the same proportion in the long run. Three phases are recognised. Increasing Returns to Scale (IRS): Output rises by a larger percentage than inputs. The cause is indivisibilities, specialisation, and internal economies. The LAC curve falls in this phase. Constant Returns to Scale (CRS): Output rises by the same percentage as inputs. Economies and diseconomies just balance each other; LAC is at its minimum and is roughly horizontal. Decreasing Returns to Scale (DRS): Output rises by a smaller percentage than inputs, mainly because of managerial diseconomies and difficulties of coordination. The LAC curve rises in this phase. The U-shaped LAC curve thus reflects the three successive phases of IRS, CRS and DRS.
Q3. Explain the behaviour of short-run cost curves (TFC, TVC, TC, AFC, AVC, ATC, MC).
Answer: In the short run, costs are classified as fixed and variable. TFC is constant at all output levels and is shown as a horizontal straight line parallel to the X-axis. TVC starts from the origin, rises slowly first (due to increasing returns), then steeply (due to diminishing returns). TC = TFC + TVC; it has the same shape as TVC but lies above it by the constant TFC. AFC = TFC/Q is a rectangular hyperbola, falling continuously. AVC is U-shaped: it falls, reaches a minimum, and rises. ATC = AFC + AVC is also U-shaped but its minimum lies to the right of the AVC minimum; the gap between ATC and AVC narrows as output rises (since AFC keeps falling). MC is U-shaped and steeper than AVC; it cuts both AVC and ATC from below at their minimum points. These shapes flow directly from the Law of Variable Proportions.
Q4. Explain the relationship between AC and MC.
Answer: The relationship between Average Cost (AC) and Marginal Cost (MC) follows from the arithmetic of averages. (i) When MC < AC, AC falls because each new unit costs less than the existing average and pulls the average down. (ii) When MC = AC, AC is at its minimum; at this point the MC curve cuts the AC curve from below. (iii) When MC > AC, AC rises because each new unit costs more than the existing average and pulls the average up. As long as MC is below AC, AC must keep falling, even if MC itself has begun to rise. Therefore the MC curve always lies below AC when AC is falling and above AC when AC is rising, intersecting it precisely at the minimum point of AC. The same logic explains the AVC–MC relationship.
Q5. Discuss long-run cost curves (LAC and LMC) and the concept of the envelope curve.
Answer: In the long run, every factor is variable, so the firm can choose any plant size. For each plant size there is a short-run average cost curve (SAC). The long-run average cost (LAC) curve is the locus of the lowest average cost at which each level of output can be produced when the firm is free to choose the optimum plant size. Hence LAC is called the envelope curve of all SAC curves; it touches each SAC at one point but never cuts it. LAC is U-shaped — falling under increasing returns to scale, flat under constant returns, and rising under decreasing returns. The long-run marginal cost (LMC) curve is also U-shaped and intersects LAC from below at the minimum point of LAC. The plant size corresponding to that point is called the optimum plant size or efficient scale, since long-run average cost is at its minimum there.
Additional Multiple-Choice Questions (MCQ)
Q1. The production function shows the relationship between:
(a) Price and quantity (b) Inputs and output (c) Cost and revenue (d) Demand and supply
Answer: (b) Inputs and output.
Q2. In the short run:
(a) All factors are variable (b) All factors are fixed (c) At least one factor is fixed (d) Output is fixed
Answer: (c) At least one factor is fixed.
Q3. Marginal Product is defined as:
(a) TP / L (b) ΔTP / ΔL (c) TP × L (d) TP − AP
Answer: (b) ΔTP / ΔL.
Q4. When MP = 0:
(a) AP is maximum (b) TP is maximum (c) AP is minimum (d) TP is zero
Answer: (b) TP is maximum.
Q5. A rational producer operates in:
(a) Stage I (b) Stage II (c) Stage III (d) Any stage
Answer: (b) Stage II.
Q6. AFC curve is:
(a) U-shaped (b) Horizontal (c) Rectangular hyperbola (d) Upward sloping
Answer: (c) Rectangular hyperbola.
Q7. MC curve cuts AVC and ATC at their:
(a) Maximum points (b) Minimum points (c) Mid-points (d) Origin
Answer: (b) Minimum points.
Q8. If output rises in greater proportion than inputs, the firm experiences:
(a) DRS (b) IRS (c) CRS (d) Diminishing returns
Answer: (b) IRS (Increasing Returns to Scale).
Q9. The long-run average cost curve is also called:
(a) Plant curve (b) Envelope curve (c) Demand curve (d) MR curve
Answer: (b) Envelope curve.
Q10. Total Cost equals:
(a) TFC − TVC (b) TFC + TVC (c) AFC + AVC (d) AC × MC
Answer: (b) TFC + TVC.
Fill in the Blanks
Q1. The technical relationship between inputs and maximum output is called the ____________.
Answer: production function.
Q2. Marginal Product = ΔTP / ____________.
Answer: ΔL (change in variable input).
Q3. The AFC curve is a ____________ hyperbola.
Answer: rectangular.
Q4. When MC is less than AC, AC ____________.
Answer: falls.
Q5. The long-run cost curve is also known as the ____________ curve.
Answer: envelope.
True or False
Q1. In the long run, all factors of production are variable.
Answer: True.
Q2. Total Fixed Cost rises as output rises.
Answer: False. TFC is constant at all output levels.
Q3. AP is maximum where AP = MP.
Answer: True.
Q4. A rational producer operates in Stage III of the Law of Variable Proportions.
Answer: False. A rational producer operates in Stage II.
Q5. Under increasing returns to scale, LAC falls.
Answer: True.
Glossary
| Term | Meaning |
|---|---|
| Production function | Technical relation between inputs and maximum output Q = f(L, K). |
| Short run | Period in which at least one factor is fixed. |
| Long run | Period in which all factors are variable. |
| Total Product (TP) | Total output produced by employing a given quantity of variable input. |
| Average Product (AP) | Output per unit of variable input, AP = TP/L. |
| Marginal Product (MP) | Addition to TP from one extra unit of variable input. |
| Law of Variable Proportions | As variable input rises with fixed inputs, TP rises at increasing rate, then diminishing rate, then falls. |
| Returns to Scale | Change in output when all inputs change in the same proportion. |
| TFC, TVC, TC | Total fixed, variable and overall costs of production. |
| AFC, AVC, ATC | Per-unit fixed, variable and total costs. |
| Marginal Cost (MC) | Addition to total cost from producing one more unit. |
| Envelope curve | Long-run average cost curve formed by tangents to all SAC curves. |
Formula Table
| Concept | Formula |
|---|---|
| Production Function | Q = f(L, K) |
| Average Product | AP = TP / L |
| Marginal Product | MPn = TPn − TPn−1 |
| Total Cost | TC = TFC + TVC |
| Average Fixed Cost | AFC = TFC / Q |
| Average Variable Cost | AVC = TVC / Q |
| Average Total Cost | ATC = TC / Q = AFC + AVC |
| Marginal Cost | MC = ΔTC / ΔQ = ΔTVC / ΔQ |
| AC–MC relation | If MC < AC, AC ↓; if MC = AC, AC minimum; if MC > AC, AC ↑ |
| AP–MP relation | If MP > AP, AP ↑; if MP = AP, AP maximum; if MP < AP, AP ↓ |
This completes the English-medium notes for ASSEB Class 11 Economics, Chapter 12 — Production and Costs. Practising the numerical schedule of TP, AP and MP and drawing rough sketches of the cost curves will help you remember the relationships discussed above. Stay with HSLC Guru for more chapter-wise notes and answer keys.