Beginning inventory, purchases, and sales for an inventory item are as follows: Sep. 1 Beginning Inventory 21 units @ $13 5 Sale 12 units 17 Purchase 23 units @ $15 30 Sale 22 units Assuming a perpetual inventory system and the first-in, first-out method: a. Determine the cost of the goods sold for the September 30 sale. b. Determine the inventory on September 30