the following purchases and sales of its only product. uses a periodic inventory system. the cost assigned to ending inventory using LIFO. Date Activities Units Acquired at Cost Units Sold at Retail May 1 Beginning inventory 178 units $10 = $1,780 May 5 Purchase 248 units $12 = $2,976 May 10 Sales 168 units $20 May 15 Purchase 128 units $13 = $1,664 May 24 Sales 118 units $21