16,000 rolls of paper were purchased and 12,500 were sold at $1.79, what is the total ending inventory?

12,500 x 1.79 to find the price but 16,000 - 12,500 to get how many were left. 
12,500 x 1.79 = $22,375 that they made from selling. 16,000 - 12,500 = 3,500 rolls left in the inventory. This question confused me so I just gave both answers.

12500*1.79=22,375 16000*1.79=28,640 Total ending inventory=28640−22,375 =6,265

Iknow one of the answers is a and maybe b but not 100% sure about b