Terence has $50 per week to spend on Subway sandwiches and milkshakes. The price of a Subway sandwich is $5 and the price of a milkshake is $4. He buys 6 sandwiches and 5 milkshakes

The marginal utility of the 6th sandwich = 25 and the marginal utility of the 5th milkshake = 24. Which of the following is true?
A) He is maximizing his utility.
B) He is not maximizing his utility and should buy more Subway sandwiches.
C) He is not maximizing his utility because he is not spending all of his income.
D) He is not maximizing his utility and should buy more milkshakes.

D