Sheridan Company markets CDs of numerous performing artists. At the beginning of March, Sheridan had in beginning inventory 2,700 CDs with a unit cost of $6. During March, Sheridan made the following purchases of CDs. March 5 1,950 @ $7 March 21 4,800 @ $9 March 13 3,600 @ $8 March 26 1,950 $10 During March 12,100 units were sold. Sheridan uses a periodic inventory system.