Hapter 7 Homework eBook Show Me How Periodic Inventory by Three Methods The units of an item available for sale during the year were as follows: an. 1 Inventory Feb. 17 Purchase July 21Purchase Nov. 23Purchase There are 1,200 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. 1,000 units at $120 1,375 units at $128 1,500 units at $136 1,125 units at $140 b. Determine the inventory cost by the last-in, first-out method c. Determine the inventory cost by the weighted average cost method