Lafonda thinks X and Y are perfect substitutes, and she likes good X three times as much as good Y.
a. Identify Lafonda's utility function. Calculate her marginal utility of X and Y by taking partial derivatives. Use your answers to calculate Lafonda's MRSXY.
b. Three bundles lie on the same indifference curve. These bundles contain 0, 2, and 4 units of X, respectively. How many units of Y might each of these bundles contain? (There is more than one correct answer. You only need to give one.)