A company purchased 300 units for $20 each on January 31. It purchased 100 units for $30 each on February 28. It sold a total of 170 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. $4,600 B. $230 C. $20,700 D. $6,900