Periodic Inventory Using FIFO, LIFO, and Weighted Average Cost Methods The units of an item availate for sale during the year were as folows Jan Aug 7 Inventory Purchase Dec. 11 Purchase 15 units af 14,000 $40,000 21 units at $4,600 96,000 18 units at $1,100 91,800 54 units $248,400 There are 17 units of the item in the physical inventory at December 31. The periodic inventory system is undeter the average cost method first-in, first-out (FIFO) method b. Last-in, first-out (FO) method Weighted average cost method