Periodic Inventory System and Inventory Costing Methods E4A. In chronological order, the inventory, purchases, and sales of a single product for a recent month are as follows. June 1 4 12 16 24 Beginning inventory Purchase Purchase Sale Purchase Units 150 400 800 1,300 Amount per Unit $30 33 36 60 39 300 1. Using the periodic inventory system, compute the cost of ending inventory, cost of goods sold, and gross margin. Use the average-cost, FIFO, and LIFO inventory costing methods. (Round unit costs to cents and totals to dollars.) Perpetual Inventory System and Inventory Costing Methods E6A. Refer to the data provided in E4A. 1. Using the perpetual inventory system, compute the cost of ending inventory, cost of goods sold, and gross margin. Use the average-cost, FIFO, and LIFO inventory costing methods. (Round unit costs to the nearest cent.)