Consider Charlie, who eats apples and bananas, and has utility function U(xA, XE) :XAXB. (a) What is the marginal utility of apples when Charlie consumes 20 apples and 5 bananas? MUA (20,5) = (b) What is the marginal utility of bananas when Charlie consumes 20 apples and 5 bananas? MUB (20, 5) = (c) What is the marginal utility of apples when Charlie consumes 10 apples and 10 bananas? MUA(10, 10) = (d) What is the marginal utility of bananas when Charlie consumes 10 apples, 10 bananas? MUB(10,10) =