Please help me with the blank one. I can not figure it out

Periodic Inventory by Three Methods The units of an item available for sale during the year were as follows: Jan. 1 Inventory Feb. 17 Purchase Jul. 21 Purchase Nov. 23 Purchase 7 units at $25 14 units at $27 15 units at $30 8 units at $30 There are 18 units of the item in the physical inventory at December 31. The periodic inventory system is used. Round average unit cost to one decimal and final answers to the nearest whole dollar, if required a. Determine the inventory cost by the first-in, first-out method. 540 b. Determine the inventory cost by the last-in, first-out method 472 c. Determine the inventory cost by the weighted average cost method. Feedback