The Shirt Shop had the following transactions for T-shirts for 2018, its first year of operations: Jan. 20 Purchased 400 units 8 $3,200 Apr. 21 Purchased 200 units 10 2,000 July 25 Purchased 280 units 133,640 Sept. 19 Purchased 90 units @ $15= 1,350 During the year, The Shirt Shop sold 810 T-shirts for $20 each. b. Compute the difference in gross margin between the FIFO and LIFO cost flow assumptions. FIFO LIFODifference Gross margin