estion Assume that Robyn wants to buy socks and once she finds out that the price per pair is $5, she decides to buy 4 pairs of socks. Which of the following is a) The marginal benefit (or marginal utility) of the 5th pair is higher than the marginal cost of the 5th pair ( b) The marginal benefit (or marginal utility) of the 4th pair must be equal to $20 c) The marginal benefit (or marginal utility) of the 5th pair must be lower than $5 O d) The marginal benefit (or marginal utility) of the first pair must be lower than $5