The Consumer's Utility Function for Goods X and Y Is

Multiple Choice

The consumer's utility function for goods X and Y is U = 3X + 15Y. Good X is placed on the x-axis and good Y is placed on the y-axis. Which of the following statements is TRUE?
I. The marginal utility of good Y is 15.
II. The MRS_XY = 5.
III. The consumer is always willing to trade away 5 units of good X for 1 unit of good Y.

A) I and II
B) II only
C) I and III
D) I, II, and III