The tool below drills the graphs and the game from your own notes.
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Unit 4 market structures, 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!
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One rule survives every market structure
Produce where marginal revenue equals marginal cost. Perfect competitors take price as marginal revenue; a monopolist's marginal revenue falls below the demand curve because selling more means lowering price on every unit. The rule is constant, and the exam tests whether your picture of it changes with the market.
The monopoly graph has a reading order, and skipping it costs
Find where marginal revenue crosses marginal cost, drop to the quantity, then rise to the demand curve for price. Charging the crossing point's height is the unit's most reliable wrong answer. Shade profit as the gap between price and average total cost times quantity, and the deadweight triangle sits between demand and marginal cost.
Price discrimination is surplus conversion, and the graph shows it
A discriminating monopolist charges buyers closer to their willingness to pay, converting consumer surplus into revenue. In the perfect case the marginal revenue curve merges with demand, output expands to the efficient quantity, and deadweight loss vanishes while consumers keep nothing. Exam prompts grade the redistribution sentence as much as the new output level.
Oligopoly is a game, and the matrix answers by elimination
With few sellers each firm's best move depends on the rival's, and the payoff matrix makes it checkable. Test each player's options one rival choice at a time: a Nash equilibrium holds where neither would switch alone. Collusion promises the joint best cell, and the dominant strategy usually betrays it.
Monopolistic competition ends flat but wasteful
Free entry erodes profit until price meets average total cost at the tangency, so long run economic profit is zero while the firm still runs below its lowest cost point. That pairing, no profit and excess capacity, with differentiation paying for the downward slope, is the exact sentence the long run question wants.
What to photograph for Imperfect Competition
Your structure graphs and payoff matrices. Related: Unit 3, photo to quiz and pricing.
Sources used on this page
- College Board, AP Microeconomics
- Monopoly
- Oligopoly
- Nash equilibrium
- Monopolistic competition
- 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
| Structure | Price versus marginal cost | Long run profit |
|---|---|---|
| Perfect competition | Equal, efficiency holds | Zero, entry erodes it |
| Monopoly | Price above, deadweight loss | Positive behind barriers |
| Perfect discrimination | Last unit at marginal cost | Maximum, surplus converted |
| Oligopoly | Depends on the game | Possible through interdependence |
| Monopolistic competition | Above, mild markup | Zero at the tangency |
| Collusion | Cartel mimics monopoly | Unstable, cheating pays |
What does AP Micro Unit 4 cover?
Monopoly, price discrimination, oligopoly with game theory, and monopolistic competition, with their graphs and efficiency verdicts.
Why is marginal revenue below price for a monopolist?
Selling one more unit requires lowering price on all units, so the extra revenue is the new sale minus the discount on everything before it.
How do I read price on a monopoly graph?
Quantity from the marginal revenue and marginal cost crossing, then price from the demand curve above it. The crossing's height is the planted wrong answer.
What is a Nash equilibrium?
A cell where neither player improves by switching alone. Find it by checking each player's best response to each rival move.
Why does monopolistic competition earn zero long run profit?
Free entry shifts each firm's demand until it just touches average total cost, leaving differentiation but no economic profit.
Can I build questions from my own Unit 4 notes?
Yes. Upload the chapter as a PDF or photograph the pages, and every question comes from those pages rather than from the wider syllabus.
Last updated: 2026-08-15