Periodic Inventory by Three Methods The units of an item avaliable for sale during the year were as follows: There are 9 units of the item in the physical inventary at December 31. The periodic inventory system is used. Round average unit cost to the nearest cent and final answers to the nearest whole dollar, if required. a. Detemmine the inventory cost by the first-in, first-out method. b. Detemine the inventory cost by the last-in, first-out method, Determine the inventory cost by the weighted average cost method