(10 points) A California distributer of sporting equipment expects to sell 8,000 cases of tennis balls during the coming year at a steady rate. - The ordering cost for each delivery is $60. - The carrying costs, based on the average number of cases in inventory, amount to $24 per year for one case. - The inventory cost is the sum of the ordering cost and carrying cost. The distributor plugs r = 8000/2 into I = 12x + 60r to obtain I = 12x + 480000/x, and differentiates to obtain d = 12 480000/ 2. She observes that di/dx = 0 when x = 200 or 200. Plugging in, she finds that when x = 200 the inventory cost is 4800, and when x = -200 the inventory cost is -4800. She deduces that the maximum inventory cost is 4800 and the minimum inventory -4800 cost is What errors did the distributor make? O A. She did not restrict to the interval of a values which have a real world meaning, and she should only have concluded that