Gladstone Limited tracks the number of units purchased and sold throughout each accounting period but applies its inventory costing method at the end of each period, as if it uses a periodic inventory system. Assume its accounting records provided the following information at the end of the annual accounting period, December 31. Transactions Beginning inventory, January 1 Transactions during the year: a. Purchase, January 30 b. Sale, March 14 ($15 each) c. Purchase, May 1 d. Sale, August 31 ($15 each) Units Unit Cost 1,200 $ 6.00 2,400 8.00 (800) 1,000 12.00 (1,600)