At the beginning of its operations in March 2020, Mastiff Supplies Ltd. began with 7,830 units of inventory that it purchased at a cost of $6.80 each. The company's purchases during March were as follows: March 13 Sales during March: 5,220 units @ $7.40 March 2 5,220 units March 20 2,940 units Mastiff Supplies uses a perpetual inventory system.