Beginning inventory, purchases, and sales for an inventory item are as follows: Sept. 1 Beginning inventory 24 units $15 5 Sale 15 units 17 Purchase 20 units $18 30 Sale 18 units Assuming a perpetual inventory system and the last-in, first-out method, determine (a) the cost of the merchandise sold for the September 30 sale and (b) the inventory on September 30. a. Cost of merchandise sold b. Inventory, September 30