The units of Product YY2 available for sale during the year were as follows: Apr 1 at Inventory units $30 each 30 w Jun 16 Purchase se units Purchase 45 units "each $37 each Sep 28 There are 15 units of the product in the physical inventory at March 31. The periodic inventory system is used. Determine the difference in gross profit between the LIFO and FIFO inventory cost systems