Periodic Inventory by Three Methods The units of an item available for sale during the year were as follows: Jan 1 Inventory 9 units @ $360 Feb 17 Purchase 18 units @ $414 July 21 Purchase 21 units @ $468 Nov 23 Purchase 12 units @ $495 There are 16 units of the item in the physical inventory at December 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. c. Determine the inventory cost by the average cost method