A company purchased 200 units for $30 each on January 31. It purchased 100 units for $40 each on February 28. It sold a total of 150 units for $110 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.) A. $6,000 B. $150 C. $12,000 D. $4,500