rj corporation has provided the following information about one of its inventory items: date transaction number of units cost per unit 1/1 beginning inventory 520 $3,320 6/6 purchase 740 $3,720 9/10 purchase 1,320 $4,120 11/15 purchase 740 $4,320 during the year, rj sold 2,880 units. what was ending inventory using the average cost flow assumption?