Given Two Goods, X and Y, Their Prices, P_X and P_Y

Multiple Choice

Given two goods, X and Y, their prices, P_X and P_Y, a consumer is in equilibrium when the last dollar spent on X yields

A) zero marginal utility for Y.
B) the same marginal utility as if all the money were spent on Y.
C) a smaller marginal utility than the last dollar spent on Y.
D) the same marginal utility as the last dollar spent on Y.