A company purchased 200 units for $40 each on January 31. It purchased 100 units for $20 each on February 28. It sold a total of 150 units for $100 each from March 1 through December 31. If the company uses the last - in, first-out inventory costing method, calculate the cost of ending inventory on December 31. (Assume that the company uses a perpetual inventory system.) O A. $9,000 OB. $6,000 C. $3,000 OD. $150