Penn Company uses a periodic inventory system. At the end of the annual accounting period, December 31, 2015, the accounting records provided the following information for product 1: Units Unit Cost Inventory, December 31, 2014 2,000 $ 5 For the year 2015: Purchase, March 21 5,000 6 Purchase, August 1 3,000 8 Inventory, December 31, 2015 4,000 Required: Compute ending inventory and cost of goods sold under FIFO, LIFO, and average cost inventory costing methods.