Microeconomics

Why every economic question is a maximisation subject to a constraint, what the cost of a choice really is, and the rule that ends every optimisation in this course.

What has to be true of a ranking before a number can stand in for it, why utility measures nothing, and the slope that survives every relabelling of it.

Maximising a preference ranking over a budget set: the tangency condition derived two ways, demand functions that fall out of it, and the corners where tangency is the wrong answer.

A price change moves the terms of trade and real purchasing power at once, and separating them says exactly when a demand curve can slope upwards.

Making responsiveness a unit-free number, why it is not the slope, how it varies along a straight line, and what it settles about revenue.

The firm as a function from inputs to output: marginal and average product, why diminishing returns is not a statement about scale, and cost minimisation as the consumer's problem with the axes relabelled.

Turning technology into a cost curve, why marginal cost cuts average cost at its minimum, and what the long-run curve is the envelope of.

What price taking assumes, why a firm produces where price equals marginal cost, when it should keep operating at a loss, and how entry drives long-run profit to zero.

Where the two curves cross, what the areas between them measure, the sense in which competition maximises their sum, and why a tax costs more than it raises.

A single seller faces the whole demand curve, so marginal revenue falls below price, output falls short of the efficient level, and the markup depends only on elasticity.

What happens between one firm and infinitely many: quantities, prices, the paradox that two firms can be enough for competition, and why cartels break.

When a cost falls on someone outside the trade, the competitive quantity is wrong, and the fixes are a tax, a property right, or a quantity limit.

What happens when one side of a trade knows more: risk aversion, the market that unravels, paying to be believed, and the tradeoff between insurance and incentives.

All markets at once: the box, the contract curve, exactly what the two welfare theorems claim, and how much of the framework survives the evidence against it.