PE 7.SA Periodic inventory using FIFO, LIFO, and weighted average cost methods OBJ. 4 The units of an item available for sale during the year were as follows: There are 17 units of the item in the physical inventory at December 31 . The periodic inventory system is used. Determine the inventory cost using (a) the first-in, first-out (FIFO) method; (b) the last-in, first-out (L.IFO) method; and (c) the weighted average cost method