I need help on this. can someone please explain how i get the right answer please

14) A sales invoice included the following information: merchandise price, $68,000; transportation, $2,400; terms 1/10, n/30, FOB shipping.Assuming that merchandise

that cost $3,600 is returned before it has been paid for, that the transportation is prepaid by the seller, and that the invoice is paid within the discount period, what is the

amount of cash that buyer pays the seller?

15) A company has 13 units in inventory at the beginning of May and paid $65 for each unit. On May 2, the company buys 18 more units and pays $67 for each unit.On May 5, the company sells 22 units for $99 each.If the company maintains its inventory using LIFO, what is the cost of merchandise sold?