Notes from Ch. 4 of Price Theory and Applications, 7th ed., by Jack Hirshleifer, Amihai Glazer, and David Hirshleifer:

4.1 Optimum of the ConsumerEdit

Budget Line the frontier of the market opportunity set of two goods that can be purchased by a consumer with a limited amount of money. For instance, if a consumer has an income (I) of $100, and she is considering purchasing good X priced at $2 () per unit and Y priced at at $1 (), her budget line and market opportunity set would be as follows: