A consumer buys only two goods, X & Y. a) If the MRS between X and Y is 2 and the marginal utility of X is 20, what is the marginal utility of Y? b) If the MRS between X and Y is 3 and the marginal utility of Y is 3, what is the marginal utility of X? c) If a consumer moves downward along an indifference curve, what happens to the marginal utilities of X and Y? What happens to the MRS?