The units of Manganese Plus available for sale during the year were as follows: Mar. 1 June 16 Nov. 28 Inventory Purchase Purchase 24 units 30 units 45 units 99 units $30 @ $31 $37 $720 930 1,665 $3,315 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