Addison, Inc. uses a perpetual inventory system. Below is information about one inventory item for the month of September. Sep. 1 Inventory 20 units at $20 4 Sold 10 units 10 Purchased 30 units at $25 17 Sold 20 units 30 Purchased 10 units at $30 If Addison uses LIFO, the September 17 cost of goods sold would be: Oa. a. $400 b. $500 c. $450 d. $600