Can someone explain me this?

High Quality Jewelers uses the perpetual inventory system. On March 3, High Quality sold merchandise for $80,000 to a customer on account with terms 4/15, n/30. The cost of goods sold was $32,000. On March 18, High Quality received payment from the customer. Calculate the amount of gross profit OA. $32,000 . $76,800 O C. $44,800 O D. $48,000