3. Cara lives in a world with two goods, apples and bananas. She has quasilinear preferences given by U(a,b)=20a+4b. (a) What are Cara's MUa and MUb ? Her MRS? (b) Suppose she has an income of I=20 and faces prices pa=2 and pb=1. What is her optimal consumption bundle? (c) What happens to her optimal bundle if her income increases to I=25 ? (d) What happens when her income instead decreases to I=1 ?