8. An operations planner, Lovell Bradley, is developing a sales and operations plan that involves back orders. The company's demand and production rates for the next four periods are as follows: Demand Period 1 2 3 4 8,200 10,000 7,000 6,600 Production 8,000 8,000 8,000 7,600 Beginning inventory at the start of period 1 is 400 units. Calculate beginning inventory, end- ing inventory, average inventory, and the back order amount, if any, for each of the next four periods