(16 points) Abigail, Bernard, Cornwallis, and Douglas each derive a distinct amount of utility from consuming apples and bananas. Initially, apples cost $2, bananas cost $1, and each person receives a weekly allowance of $20 to spend. For each of the four sets of preferences described below, calculate the compensating variation if the price of apples rises to $5. (a) (4) Abigail: U(a, b) = a + 2b (b) (4) Bernard: U(a, b) = 2a + b (c) (4) Cornwallis: U(a, b) = b - a (d) (4) Douglas: U(a, b) = min(a, 3b)