Smith Company had the following purchases and inventory levels during September. Use this data to calculate the cost of goods sold expense using the FIFO method. September 1 Beginning Inventory 15 units at $20 each September 10 Purchase 20 units at $25 each September 20 Purchase 25 units at $28 each September 30 O $825 Ending Inventory 30 units $750 O$675 O $600