In the short run, a firms total costs of producing 100 units of output equal $10,000. If it produces one more unit, its total costs will increase to $10,150. (See pages 491-492.) a. What is the marginal cost of the 101st unit of output? b. What is the firms average total cost of producing 100 units? c. What is the firms average total cost of producing 101 units? d) How is it that the average cost is increasing?