Addison, Inc. uses a perpetual inventory system. The following 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 Average cost method, the cost of the ending merchandise inventory on September 30 is