At the beginning of its operations in March 2020, Mastiff Supplies Ltd. began with 8,010 units of inventory that it purchased at a cost of $6.90 each. The company's purchases during March were as follows: March 13 Sales during March: 5,340 units @ $7.50 March 2 5,340 units March 20 2,970 units Mastiff Supplies uses a perpetual inventory system.