Beginning inventory, purchases, and sales for an inventory item are as follows: Sep. 1 Beginning Inventory 26 units @ $19 5 Sale 15 units 17 Purchase 27 units @ $20 30 Sale 28 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