Carol Corp. purchased inventory as follows: March 3 500 units at $19 March 4 300 units at $21 March 7 180 units at $23 On March 5, Carol sold 650 units for $19 each. The average unit cost to be used for the cost of goods sold on March 5, in a perpetual inventory system, is O $24.31. $19.75. O $20.35. O $16.63.