This a question from my textbook:
Andy purchases only 2 goods, apples (q1) and kumquats(q2). He
has an income of $40 and can buy apples at a $2 per pound and kumquats at $4 per pound. His utility function is U(q1,q2)=3q1+5q2.What is his marginal utility for apples, and what is his marginal utility for kumquats? What bundle of apples and kumquats should he purchase to maximize his utility? Why?