E6-14 The units of an item available for sale during the year were as follows: Jan. 1 Inventory 27 units at $120 Feb. 17 Purchase 54 units at $138 July 21 Purchase 63 units at $156 Nov. 23 Purchase 36 units at $165 There are 50 units of the item in the physical inventory at December 31. The periodic inventory system is used. Determine the inventory cost by (a) the firstin, first-out method, (b) the last-in, first-out method, and (c) the average cost method