costs, revenue, and profits

Define total revenue (TR) and give the formula.

Total revenue is the money a firm receives from selling its output. TR = price × quantity sold (TR = P × Q).

Define average revenue (AR) and give the formula.

Average revenue is revenue per unit sold. AR = TR ÷ Q. In imperfect competition, AR = price.

Define marginal revenue (MR).

Marginal revenue is the change in total revenue from selling one extra unit of output.

What is the relationship between AR and demand?

The AR curve is the same as the firm’s demand curve, showing the price it can charge at each output level.

In imperfect competition, what is the typical shape of AR and MR and why?

AR is downward sloping because to sell more output the firm must lower price. MR lies below AR because extra units are sold at a lower price, reducing revenue from previous units.

When is MR positive, zero and negative, and what happens to TR in each range?

MR > 0: TR is rising. MR = 0: TR is maximised. MR < 0: TR is falling as output increases.

What is the profit-maximising condition using MR and MC?

A profit-maximising firm produces at the output level where marginal revenue = marginal cost (MR = MC). If MR > MC, increase output; if MR < MC, reduce output.

On a diagram with a downward-sloping AR, where is TR maximised and how is this shown?

TR is maximised where MR = 0. On the AR–MR diagram, this is the output where the MR curve crosses the horizontal axis; on a separate TR curve it is the peak of the TR curve.

Explain why MR falls faster than AR in imperfect competition.

To sell extra units, the firm cuts price on all units, so the gain in revenue from the extra unit is partly offset by lower revenue on previous units. This makes MR fall faster than AR.

Evaluation: why might firms not always maximise profit at MR = MC?

Firms may aim for revenue maximisation, growth or market share instead of strict profit maximisation. Managers may satisfice due to principal–agent problems and other stakeholder objectives.

what determines how much a price cut will change TR?

The impact of a price cut on TR depends on price elasticity of demand. If demand is elastic, a price cut raises TR; if inelastic, a price cut lowers TR.

Define fixed costs with two examples.

Fixed costs do not vary with output in the short run. Examples: rent, salaried management, insurance.

Define variable costs with two examples.

Variable costs change directly with output. Examples: raw materials, piece-rate wages, components, energy use in production.

Give formulas for total cost (TC), total fixed cost (TFC), and total variable cost (TVC).

TC = TFC + TVC. TFC is the sum of all fixed costs; TVC is the sum of all variable costs.

Define average total cost (ATC or AC) and give the formula.

Average cost is cost per unit of output. AC = TC ÷ Q.

Define average fixed cost (AFC) and its formula and shape.

AFC = TFC ÷ Q. As output increases, AFC falls continuously, giving a downward-sloping AFC curve.

Define average variable cost (AVC) and give its typical shape.

AVC = TVC ÷ Q. It is typically U-shaped: initially falls due to increasing returns, then rises as diminishing marginal returns set in.

Define marginal cost (MC).

Marginal cost is the change in total cost from producing one extra unit of output.

What is the relationship between MC and AC/AVC at their minimum points?

MC cuts both AC and AVC at their minimum points. When MC < AC, AC falls; when MC > AC, AC rises.

Explain why short-run AC and MC curves are U-shaped.

At low output, increasing marginal returns to variable factors reduce marginal and average costs. At higher output, diminishing marginal returns raise marginal and average costs, creating a U-shape.

Distinguish short run from long run in cost analysis.

Short run: at least one factor is fixed, so firms face diminishing returns and U-shaped SRAC. Long run: all factors are variable and firms can choose the most efficient scale of plant.

What is the long-run average cost (LRAC) curve and how is it derived?

LRAC is the lowest possible average cost for each output level when all inputs are variable. It is the envelope of the firm’s short-run average cost (SRAC) curves.

On a cost diagram, where is the shutdown price in the short run?

The short-run shutdown price is where price = minimum AVC. Below this price, the firm stops producing because it cannot cover variable costs.

On a cost diagram, what is the long-run break-even condition?

In the long run, the firm must cover all costs and earn normal profit, so price = minimum AC (P = AC).

why might firms continue to produce in the short run even if they are making losses?

As long as P ≥ AVC, firms cover variable costs and contribute something towards fixed costs. They may expect demand to recover or be cross-subsidised by profits elsewhere.

Define economies of scale.

Economies of scale are the cost advantages a firm experiences as it increases scale of production in the long run, leading to falling long-run average cost.

Define diseconomies of scale.

Diseconomies of scale are the disadvantages of large-scale production that cause long-run average cost to rise as output increases beyond some point.

Explain how economies of scale are shown on a LRAC diagram.

Economies of scale are shown by the downward-sloping part of the LRAC curve as output rises. LRAC falls because larger scale allows more efficient production.

Explain how diseconomies of scale are shown on a LRAC diagram.

Diseconomies are shown by the upward-sloping part of LRAC at high output levels. Beyond the minimum efficient scale, further expansion raises average costs.

Define minimum efficient scale (MES).

MES is the lowest level of output at which long-run average cost is minimised. It is the output range over which a firm fully exploits economies of scale.

Give four internal economies of scale with brief explanations.

1) Technical: larger firms use more efficient, specialised capital and production techniques. 2) Managerial: specialist managers improve organisation and productivity. 3) Purchasing: bulk buying of inputs lowers average input costs. 4) Financial/marketing: cheaper finance and spreading advertising over more units reduces unit cost.

Define external economies of scale with an example.

External economies of scale occur when growing size of the industry (not the firm) lowers average cost for all firms. Example: a skilled local labour pool or shared infrastructure in an industry cluster.

Give three possible causes of diseconomies of scale.

1) Communication problems in very large organisations, leading to delays and errors. 2) Coordination and control difficulties across many plants and managers. 3) Lower worker motivation or alienation in large, impersonal firms.

How can economies of scale affect market structure and competition?

Strong economies of scale can create high minimum efficient scale, favouring large firms and concentrated markets. This may act as a barrier to entry and reduce contestability.

why might some firms choose to stay small despite potential economies of scale?

Smaller firms can avoid internal diseconomies, stay flexible and focus on niche markets with high margins. They may benefit from external economies while keeping internal costs low.

under what conditions might diseconomies of scale become significant?

When firms expand rapidly via mergers, span of control grows and cultures clash, raising coordination costs. Regulatory, bureaucracy and communication burdens also increase with size.

Define profit in economics and give the formula.

Profit is total revenue minus total cost, where total cost includes both explicit and implicit (opportunity) costs. Profit = TR − TC.

Define normal profit.

Normal profit is the minimum level of profit needed to keep a firm in its current line of production in the long run. It is where TR = total cost, including the opportunity cost of capital and enterprise.

Define supernormal (abnormal) profit.

Supernormal profit is any profit above normal profit. It occurs when TR > total cost, including opportunity costs.

Define economic loss.

A loss occurs when total revenue is less than total cost (TR < TC). The firm earns less than normal profit.

Show normal profit on a cost–revenue diagram for a firm.

Normal profit occurs where AR = AC at the profit-maximising output (MR = MC). The AR curve just touches AC, so there is no “profit rectangle” above AC.

Show supernormal profit on a diagram and how to calculate it.

At the profit-maximising output (MR = MC), if AR > AC, the firm earns supernormal profit. The profit area is (AR − AC) × Q, shown as a rectangle between AR and AC over that output.

Show a loss on a diagram and what it means.

At MR = MC, if AR < AC, the firm makes a loss per unit. The loss area is (AC − AR) × Q, the rectangle between AC and AR.

Why is normal profit considered a cost of production in economic theory?

Normal profit is the opportunity cost of using the entrepreneur’s capital and skills in this firm rather than elsewhere. It is included in the firm’s long-run average cost.

Explain the short-run shutdown condition in terms of profit and cost.

In the short run a firm continues producing if TR covers TVC (P ≥ AVC), even if it makes an economic loss overall. If P < AVC, it shuts down because it cannot cover variable costs.

Explain the long-run exit condition for a firm.

In the long run, if a firm cannot at least earn normal profit (TR < TC at every output), it will leave the market. Remaining would not cover the opportunity cost of resources.

Give two reasons why profit is important for firms and the wider economy.

1) Profit is a key source of internal finance for investment and R&D (retained profits). 2) Supernormal profits signal profitable markets, attracting entry and reallocating resources to high-value uses.

why might very high supernormal profits be criticised?

They may indicate market power and consumer exploitation through high prices. Regulators may intervene if profits reflect anti-competitive behaviour rather than efficiency.

why might firms accept lower profit margins in the short run?

To gain market share, deter entry or survive a downturn, firms may price aggressively and accept lower or zero supernormal profit. Stakeholder objectives (jobs, reputation) can also constrain profit maximisation