Classifying costs: FC, VC, TC, AC
Classify costs correctly. Fixed costs (FC) do not change with output in the short run — rent, insurance, permanent salaries, loan interest — so the total stays the same. Variable costs (VC) change with output — raw materials, packaging, piece-rate wages — so the total rises. Total cost = fixed costs + variable costs. Average (unit) cost = total cost divided by output. The classic trap is swapping them: rent is fixed; production wages and materials are variable.
Contribution and break-even output
Break-even is the output where total revenue equals total cost — neither profit nor loss. Contribution per unit = selling price minus VARIABLE cost per unit (not total cost) — what each unit puts towards fixed costs, then profit. Break-even output = fixed costs divided by contribution per unit, so it is in UNITS. Example: fixed costs 4000, price 9, variable cost 5, so contribution is 9 minus 5 = 4 and break-even is 4000 divided by 4 = 1000 units.
Economies and diseconomies of scale
Scale changes a firm's AVERAGE (unit) cost. Economies of scale are cost advantages of producing on a larger scale — average cost FALLS as output rises, not just a bigger total. Types: purchasing (bulk discounts), marketing (advertising spread wider), financial (cheaper borrowing), managerial, technical. Diseconomies arise when a firm grows too large and average cost RISES — poor communication and weak coordination. The point is the effect on UNIT cost.
Drawn from real examiner reports.
Break-even output is units, not money
Break-even output is a QUANTITY — a number of units — because it is fixed costs divided by contribution per unit. Candidates often write it as a money figure when the question asks for output. Keep them apart: break-even revenue = break-even output times selling price. If output is 500 units at a price of 120, break-even revenue is 60000 — but the OUTPUT answer is 500 units.
June 2022 P12 Q3(b); June 2023 P12 Q1(b): break-even output was expressed as a money value rather than in units.
Contribution vs revenue vs profit
Three figures are mixed up. Revenue = selling price times quantity — money coming IN, before costs, so NOT profit. Contribution per unit = selling price minus VARIABLE cost per unit; subtracting total cost does not give contribution. Profit = revenue minus total cost, or total contribution minus fixed costs. "Sold 13500, so made 13500 profit" confuses revenue with profit.
June 2023 P12 Q1(c): the revenue-contribution-profit relationships were not secure.
Break-even assumes all output is sold
Break-even analysis is a simplified model; candidates lose marks treating it as exact. Its assumptions: everything produced is SOLD; the selling price stays constant; the variable cost per unit stays constant; and it relies on estimated data. A common error is arguing a higher price simply raises profit, forgetting it usually cuts quantity sold.
June 2023 P12 Q1(c): candidates focused on higher prices reducing sales while forgetting that a break-even chart assumes all output is sold.
Margin of safety uses ACTUAL output
Margin of safety = ACTUAL output minus break-even output — how far current sales can fall before a loss. A common error is using MAXIMUM output minus break-even instead of actual, which overstates it. It is in units, so do not give a money value or add the two figures. Example: with break-even 1000 and actual output 1500, the margin of safety is 1500 minus 1000 = 500 units.
June 2022 P11 Q2(b): many took margin of safety as maximum output minus break-even output, not actual output minus break-even output.
Economies of scale lower UNIT cost
Economies of scale mean lower AVERAGE (unit) cost as output grows — NOT simply lower total cost. As output rises total cost usually rises too; what falls is the cost PER UNIT, as fixed costs and discounts spread over more output. Saying "costs are lower" without specifying unit cost misses the mark. Name the source — a bulk discount or cheaper borrowing.
June 2022 P22 Q1(b): the link to lower average (unit) cost was routinely missing; candidates said costs are lower when only unit costs fall.
Do not swap fixed and variable costs
Fixed and variable costs are regularly swapped. Fixed costs do not change with output — rent, insurance, salaries. Variable costs change with output — raw materials, piece-rate wages. When a FIXED cost is asked for, giving a variable one such as wages earns no mark. Test each: does the cost rise if one more unit is made? If yes it is variable; if not, fixed.
November 2022 P12 Q4(b): variable costs (wages, raw materials) were confused with fixed costs.
Break-even chart plans ahead, not looks back
A break-even chart is a forward PLANNING tool, not a record of past performance. It lets a firm predict, before committing, the output needed to break even, the profit or loss at a given output, and the effect of changing price or costs. Treating it as a report of what already happened misses its purpose. Focus on the decisions it supports in advance.
June 2022 P21 Q2(a): the break-even chart was treated as a record of past performance rather than a forward planning tool.
Evaluation needs a supported judgement
The 6-mark "Do you think...? Justify" carries the AO4 marks. The top marks need a SUPPORTED judgement: decide and say WHY one side outweighs the other here, not just list both sides. Hooks: how close to break-even, the margin of safety, whether the assumptions hold.
Mirror arguments are credited once
"Option A has low costs while B has high costs" is ONE point, not two — a mirror argument earns a single mark; so does "job has no economies of scale while batch has some". For a genuine second point, develop a distinct reason — a different cost, risk or benefit.
Explain WHY each element helps, do not list
Asked how a break-even chart helps, do not just list its parts — explain their USE: the break-even point shows the minimum output to avoid a loss; the gap between the lines shows profit or loss. Listing is knowledge; explaining the use earns the higher marks.
Every business has costs, and you must be able to classify them.
| Cost | What it is | Examples | As output rises... |
|---|---|---|---|
| Fixed costs (FC) | do not change with output (short run) | rent, insurance, manager salaries, loan interest | total stays the same |
| Variable costs (VC) | change directly with output | raw materials, packaging, piece-rate wages | total rises |
| Total cost (TC) | FC + VC | — | rises (because VC rises) |
| Average cost (AC) | cost per unit = total cost / output | — | usually falls then rises |
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