What does a cost elasticity of one mean?

Average cost stops changing with output, near its minimum.

Can learning curves and economies of scale coexist?

Yes, they have different sources and can add up.

Why is a natural monopoly regulated?

A single producer may overcharge, so price or output is supervised.

How do economies of scope differ from economies of scale?

Scope comes from sharing inputs across products; scale comes from more output of one product.

S5 Economics paper 2: cost curves and scale

2026-11-10

Tutor Prep Guide · S5 Economics Cost Curves

Ten items handle substitution into a cost curve, the minimum point and minimum efficient scale, then separate learning curves, natural monopoly and economies of scope.

Direct answers　Items 01 to 03 substitute into the cost curve, 04 to 06 compute percentage gaps, firm numbers and cost elasticity, 07 to 09 distinguish learning curves, natural monopoly and scope economies, and 10 corrects short-run and long-run confusion.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S5 Economics Long-run Cost and Economies of Scale
Level	S5

02　Questions (10 items)

FoundationA firm has long-run average cost 3,600 / Q + 16 + 0.04Q. Find average cost at Q = 300.
FoundationFor the same cost curve, at what output is long-run average cost lowest?
FoundationFor the same curve, find average cost at Q = 150.
IntermediateHow much higher is average cost at 150 units than at 300 units?
IntermediateMinimum efficient scale is 300 units and market demand is 900 units. How many firms can reach minimum cost?
IntermediateOutput rises 25 per cent and average cost falls 10 per cent. Find the absolute cost elasticity with respect to output.
ChallengeA firm cuts cost through accumulated production experience rather than current scale. What is this called?
ChallengeIn an industry long-run average cost keeps falling across the whole range of market demand. Which market structure is most likely?
ChallengeA firm makes two products and shares warehouses and managers, lowering unit cost. What is this called?
Error redoA student calls any fall in short-run average cost economies of scale. Why is that inaccurate?

03　Answers and one-line notes

#	Answer	One-line note
1	$40 (12 + 16 + 12).	Substitute term by term: 12 spread, 16 constant, 12 variable.
2	300 units.	It is lowest where the falling spread term offsets the rising variable term.
3	$46 (24 + 16 + 6).	Halving output lifts the spread part from 12 to 24.
4	15 per cent ((46 – 40) / 40).	Use the minimum-point average cost as the denominator.
5	Three firms (900 / 300).	Divide market demand by minimum efficient scale.
6	0.4 (10 per cent / 25 per cent).	Below one means economies of scale still exist but are modest.
7	The learning curve (learning by doing).	The learning curve depends on cumulative output; economies of scale depend on current output.
8	Natural monopoly.	One firm can supply the market most cheaply, blocking entry.
9	Economies of scope.	Savings from shared inputs, distinct from simply producing more of one good.
10	A short-run fall often just spreads fixed cost; economies of scale need the long run with all inputs variable.	In the short run plant size is fixed, so scale cannot really change.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Book an Economics tutor Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.