The units of Manganese Plus available for sale during the year were as follows: Mar. 1 Inventory 21 units @ $31 $651 June 16 Purchase 29 units @ $35 1,015 Nov. 28 Purchase 40 units @ $38 1,520 90 units $3,186 There are 12 units of the product in the physical inventory at November 30. The periodic inventory system is used. Round answers to the nearest whole dollar. a. Determine the inventory cost by the FIFO method. $ b. Determine the inventory cost by the LIFO method. $ c. Determine the inventory cost by the average cost methods. $