Periodic inventory by three methods The units of an item available for sale during the year were as follows: Jan. 1 Inventory 2,800 units at $7 Feb. 17 Purchase 3,000 units at $9 Jul. 21 Purchase 3,100 units at $11 Nov. 23 Purchase 1,100 units at $13 There are 1,300 units of the item in the physical inventory at December 31. The periodic inventory system is used. This information has been collected in the Microsoft Excel Online file. Open the spreadsheet, perform the required analysis, and input your answers in the questions below. Open spreadsheet a. Determine the inventory cost by the first-in, first-out method. Round your answer to the nearest dollar. $ 18,000 X b. Determine the inventory cost by the last-in, first-out method. Round your answer to the nearest dollar. $ c. Determine the inventory cost by the weighted average cost method. Round your answer to the nearest dollar. $