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 the weighted average cost method, calculate the inventory balance at the end of September