Periodic Inventory by Three Methods The units of an item available for sale during the year were as follows: Jan. 1 Inventory 4 units $50 Feb. 17 Purchase 6 units @ $51 July 21 Purchase 14 units o $53 Nov. 23 Purchase 6 units $55 There are 4 units of the item in the physical inventory at dotember 31. The periodic Inventory system is used. a. Determine the inventory cost by the first-in, first-out method. b. Determine the inventory cost by the last-in, first-out method.