Cost and Revenue Analysis: Cost Concepts, Cost Curves, Revenue Curves and Profit Questions

Question 1

Define fixed cost.

Accepted Answer

Fixed cost is the cost that does not change with change in output in the short run, such as rent and insurance.

Question 2

Define variable cost.

Accepted Answer

Variable cost is the cost that changes with output, such as raw materials and wages of casual labour.

Question 3

What is marginal cost?

Accepted Answer

Marginal cost is the additional cost incurred in producing one more unit of output.

Question 4

Define total revenue (TR).

Accepted Answer

Total revenue is the total income from selling output and is equal to price multiplied by quantity sold (TR = P×Q).

Question 5

What is average revenue (AR)?

Accepted Answer

Average revenue is revenue per unit of output and is equal to TR divided by quantity (AR = TR/Q).

Question 6

State the profit maximisation condition.

Accepted Answer

Profit is maximised when marginal revenue equals marginal cost (MR = MC) and MC is rising.

Question 7

Explain cost concepts: fixed cost, variable cost and total cost.

Accepted Answer

Fixed cost (TFC) does not change with output in the short run, e.g., rent. Variable cost (TVC) changes with output, e.g., raw materials. Total cost (TC) is the sum of fixed and variable costs, i.e., TC = TFC + TVC. As output increases, TC rises mainly because TVC rises while TFC remains constant.

Question 8

Explain average cost (AC), average variable cost (AVC) and average fixed cost (AFC).

Accepted Answer

Average fixed cost is TFC/Q and it falls continuously as output increases. Average variable cost is TVC/Q and is generally U-shaped due to law of variable proportions. Average cost is total cost per unit, AC = TC/Q, and it equals AFC + AVC. AC is also U-shaped and lies above AVC because it includes AFC.

Question 9

Explain relationship between MC and AC.

Accepted Answer

When MC is less than AC, AC falls because an additional unit costs less than the average. When MC is greater than AC, AC rises. Therefore MC intersects AC at the minimum point of AC. This relationship helps explain the U-shape of AC curve in the short run.

Question 10

Explain TR, AR and MR with relations.

Accepted Answer

Total revenue (TR) is total income from sales (TR = P×Q). Average revenue (AR) is revenue per unit (AR = TR/Q) and is generally equal to price. Marginal revenue (MR) is additional revenue from selling one more unit (MR = ΔTR/ΔQ). Under perfect competition AR = MR; under imperfect competition MR lies below AR.

Question 11

Differentiate between revenue curves under perfect competition and monopoly.

Accepted Answer

Under perfect competition, the firm is a price taker, so AR is constant and equal to price; therefore AR = MR and the demand curve is horizontal. Under monopoly, the firm faces a downward sloping demand curve, so AR slopes downward and MR lies below AR because price must be reduced to sell more units.

Question 12

Explain break-even point and its usefulness.

Accepted Answer

Break-even point is the level of output or sales at which total revenue equals total cost (TR = TC), so there is no profit and no loss. It is useful for planning minimum sales needed to avoid loss, comparing alternative projects and understanding how profits change with changes in output and costs.

Question 13

Explain short run cost curves. Describe shapes of AFC, AVC, AC and MC and their relationships.

Accepted Answer

In the short run, at least one factor of production is fixed, so costs are divided into fixed and variable costs. The main short run cost curves are AFC, AVC, AC and MC.

**AFC (Average Fixed Cost):** AFC = TFC/Q. Since TFC is constant, AFC falls continuously as output increases. The AFC curve is a continuously declining curve.

**AVC (Average Variable Cost):** AVC = TVC/Q. AVC is generally U-shaped due to the law of variable proportions. Initially, increasing returns reduce per unit variable cost, so AVC falls; later, diminishing returns increase variable cost per unit, so AVC rises.

**AC (Average Cost):** AC = TC/Q = AFC + AVC. AC is also U-shaped. In the beginning, both AFC and AVC fall, so AC falls. After a point, AVC rises; even though AFC keeps falling, the rise in AVC dominates and AC rises.

**MC (Marginal Cost):** MC = ΔTC/ΔQ = ΔTVC/ΔQ. MC is also U-shaped due to increasing and diminishing returns.

**Relationships:** MC cuts AVC and AC at their minimum points. When MC < AC, AC falls; when MC > AC, AC rises; thus MC = AC at AC minimum. Similar relation holds between MC and AVC. These relationships are important for output and pricing decisions.

Question 14

Explain revenue concepts TR, AR and MR. Discuss their relationship under perfect competition and monopoly.

Accepted Answer

Revenue is the income received from sale of output. The main revenue concepts are total revenue, average revenue and marginal revenue.

**Total Revenue (TR):** TR is the total income from sales and is equal to price multiplied by quantity sold (TR = P×Q).

**Average Revenue (AR):** AR is revenue per unit of output. It is calculated as AR = TR/Q and is generally equal to price.

**Marginal Revenue (MR):** MR is additional revenue obtained from selling one more unit. It is calculated as MR = ΔTR/ΔQ.

**Relationship under perfect competition:** A perfectly competitive firm is a price taker. Price remains constant for all units sold, so AR is constant and equals price. Since each additional unit is sold at the same price, MR also equals price. Hence, under perfect competition, AR = MR = Price and the AR curve is horizontal.

**Relationship under monopoly:** A monopolist faces a downward sloping demand curve. To sell more units, the monopolist must reduce price. Therefore AR falls as output increases and MR lies below AR because MR reflects the price reduction on previous units as well. Thus, under monopoly, AR is downward sloping and MR is below AR.

These relationships help in determining output and profit-maximising price under different market structures.

Question 15

Explain profit maximisation. State the conditions of profit maximisation and explain break-even point.

Accepted Answer

Profit maximisation means choosing the level of output at which the difference between total revenue and total cost is maximum. Profit (π) is calculated as π = TR − TC.

**Conditions of profit maximisation:**
1. **Necessary condition:** MR = MC. This means the additional revenue from selling one more unit equals the additional cost of producing it. If MR > MC, producing one more unit increases profit; if MR < MC, producing more reduces profit.
2. **Sufficient condition:** MC must cut MR from below, i.e., MC should be rising at the equilibrium output. This ensures that the MR=MC point corresponds to maximum profit and not minimum.

**Break-even point (BEP):** Break-even point is the level of output or sales at which total revenue equals total cost (TR = TC). At this point, the firm earns neither profit nor loss. BEP is useful for planning because it shows the minimum sales needed to avoid loss and helps management analyse how profits change with output, costs and price.

Thus, MR=MC rule guides profit maximisation and break-even analysis helps in practical planning and control.

Cost and Revenue Analysis: Cost Concepts, Cost Curves, Revenue Curves and Profit

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