Microeconomics

marginal utility is the value gained from having one more of something, such as another dollar or car.

supply and demand is how production and consumption change in response to price.

Consumer demand changes with price. For substitute and complementary goods, a price change for one good can impact demand for another.

Price elasticity measures how consumer demand responds to price changes. Price Elasticity of Demand (PED) is used to quantify it mathematically. Cross-Price Elasticity of Demand (CPED) does so across substitute goods.

Profit is total revenue - total costs. The costs include cost of production.