Use the following information for the month of May: May 1 17822 Beginning Inventory 20 units @ $19 Purchases 90 units @ $20 Sales 15 units Purchases 10 units @ $22 29 Sales 40 units Assuming that a periodic inventory system is used, what is ending inventory on a FIFO basis? Select one: O a. $720 O b. $680 O c. $1,280 O d. $1,320