Q5. A firm sells two products, x and y. The demand for each product are: x = 100 - Px - Py and y = 200 - 2Py - Px The joint-cost function is: TC = xtacyty- i. How many units of x and y should be sold to obtain a relative maximum profit for the monopolist? Use the second-order derivative test to justify the answer. [9 marks] ii. Are these goods substitutable or complemetary? [6 marks]