Assume a periodic inventory costing method. (a) Compute the cost of the ending inventory and the cost of goods sold under (1) FIFO, (2) LIFO, and (3) average-cost. (b) Which costing method gives the highest ending inventory? The highest cost of goods sold? Why? (c) Explain why the average cost is not $6. (d) For Extra Credit , up to 5 points, assume a perpetual inventory costing system. Compute the ending inventory and cost of goods sold as if half of the sales were made after August 12 and before August 23; and half of the sales were made after August 23 and before August 31. Show all your work and calculations. Discuss why the COGS and EI are different values under the perpetual method. DateExplanationUnitsUnit CostTotal Cost1-AugBeginning inventory120$5$60012-AugPurchase 370$6$2,22023-AugPurchase 500$7$3,50031-AugEnding Inventory160