Suppose that two units of X and eight units of Y give a consumer the same utility as four units of X and two units of Y. Over this range:
a. What is the marginal rate of substitution over this range of consumption?
b. If the consumer obtains one more unit of X, how many units of Y must be given up in order to keep utility constant?
c. If the consumer obtains one more unit of Y, how many units of X must be given up in order to keep utility constant?