Jan. 20 Apr. 21 July 25 Purchased 390 units Purchased 110 units Purchased Sept. 19 Purchased 230 units 90 units $3 $1,170 $4-> 8 $6- 1,380 440 8 $8-> 720 During the year, The Shirt Shop sold 620 T-shirts for $13 each. Required a. Compute the amount of ending inventory The Shirt Shop would report on the balance sheet, assuming the following cost flow assumptions: (1) FIFO, (2) LIFO, and (3) weighted average. b. Compute the difference in gross margin between the FIFO and LIFO cost flow assumptions.