Not sure if I did this correctly

The units of Manganese Plus available for sale during the year were as follows: Mar. 1 Inventory 16 units @$30 $480 June 16 Purchase 30 units @$35 1,050 Nov. 28 Purchase 45 units @$39 1,755 91 units 3,285 There are 15 units of the product in the physical inventory at November 30. The periodic inventory system is used. Determine the difference in gross profit between the LIFO and FIFO inventory cost systems. Enter all numbers as positive numbers. FIFO Cost of Goods Sold $ 585 LIFO Cost of Goods Sold 450 Difference 135