l. [20 marks] (a) Consider Kuhn with the utility function, U = 1 / xy. Let Px and PJ) be the prices of goods x and y respectively and M be income. Suppose that Kuhn buys good at from a store that offers him the following deal: buy 96 units, get ax units free, where a > 0. (3) Find an expression for Kuhn's optimal consumption of good 36 as a mction of Px, P3,, and M. (b) Using the function in {a}, intuitively explain why a seller of good 36 will offer the deal above