Once that is automatic, the curves stop being shapes to memorise and become a record of decisions.
WeSolve+ reads the whole document and writes the questions for you
Upload your PDF, photograph your notebook, or point the camera. WeSolve+ writes questions from that material, explains why each answer is right, reads the chapter back to you as a podcast, and remembers every item you missed until you own it.
The tool below is a small browser-only tool and it is not WeSolve+: paste a few lines and text rules turn them into cards on the spot. The real app, the one that uses AI, is behind the link above.
Cost concepts, from your own notes
This is a browser-only tool, and that is all it isIt splits the text you paste by rule, and nothing else. WeSolve+ is a different thing entirely: it reads your whole PDF with AI, writes the reasoning behind every question, speaks the chapter back to you, and remembers what you missed so it can return it. Try the real app now, free!
This tool splits the text you paste by rule and returns cards. It cannot draw or read a curve, so it works on the definitions you already wrote down.
Sunk costs are irrelevant, and that feels wrong
Money already spent and unrecoverable cannot be changed by any decision you make now, so it does not belong in the comparison. Everyday reasoning insists otherwise, which is why questions include a large past expenditure specifically to see whether it pulls your answer. Noticing the trap is the skill.
Marginal cost cuts average cost at its minimum, and here is why
While the next unit costs less than the running average, the average falls. When it costs more, the average rises. So the two curves meet exactly where the average stops falling. Understanding that sentence means you never have to remember the picture, because you can reconstruct it.
Price taker is a claim about the firm's demand curve
Under perfect competition a single firm cannot move the market price, so the demand curve it faces is horizontal even though the market demand curve slopes down. Holding both pictures at once, and knowing which one a question is showing you, prevents a very common confusion.
Shutdown is a different test from exit
In the short run a firm keeps producing while price covers average variable cost, because fixed costs are paid either way. In the long run it leaves if it cannot cover everything. Two tests, two time horizons, and questions state which horizon they mean precisely because the answers differ.
Zero economic profit is not zero accounting profit
It means the firm is earning exactly what its resources could earn elsewhere, opportunity cost included. Students who read it as a business making nothing conclude that long run equilibrium is a disaster, when it is a description of a market where nothing more is to be gained by entering or leaving.
What to photograph for Production, Cost and the Perfect Competition Model
Curves with your shift arrows and a reason beside each. Related: Unit 2, quiz options and pricing.
Sources used on this page
- College Board, AP Microeconomics
- Marginal cost
- Perfect competition
- Economies of scale
- Opportunity cost
- Active recall
- Spaced repetition
- Testing effect
- Forgetting curve
- Generation effect
- Judgment of learning
- Metacognition
- Desirable difficulty
- Distributed practice
- Formative assessment
- Flashcard
- Cloze test
- Multiple choice
- Test (assessment)
- Educational assessment
- Advanced Placement
- Curriculum
- Study skills
- Study guide
- Note-taking
- Overlearning
- Instructional scaffolding
- Item analysis
- Mastery learning
| Question | Use | Do not use |
|---|---|---|
| Produce one more unit? | Marginal cost against marginal revenue | Average total cost |
| Keep operating today? | Price against average variable cost | Fixed costs |
| Stay in this industry? | Price against average total cost | Short run reasoning |
| Was the factory worth it? | Nothing, it is sunk | Any current decision |
| Where is efficiency? | Minimum average total cost | Any single point |
| Long run profit? | Zero economic profit | Accounting profit |
What is AP Microeconomics Unit 3?
Production, Cost and the Perfect Competition Model: production functions, cost curves, profit maximisation and firm decisions in the short and long run.
Why are sunk costs irrelevant?
Because they cannot be changed by any current decision. Questions include a large past expenditure specifically to see whether it pulls your answer.
Why does marginal cost cross average cost at the minimum?
Because while the next unit costs less than the running average, the average falls; when it costs more, the average rises. They meet where the fall stops.
Why is the firm's demand curve horizontal?
Because a price taker cannot move the market price. The market demand curve still slopes down, and knowing which picture you are shown prevents confusion.
What is the difference between shutdown and exit?
Shutdown is short run and compares price to average variable cost. Exit is long run and compares price to average total cost.
Does zero economic profit mean the firm earns nothing?
No. It means the resources earn exactly what they could earn elsewhere, opportunity cost included.
Last updated: 2026-08-15