Can someone explain step by step how to work this problem out?

54. A company purchased $1,800 of merchandise on July 5 with terms 2/10, n/30. On July 7, it returned $200 worth of merchandise. On July 8, it paid the full amount due. The amount of the cash paid on July 8 equals: A. $200. B. $1,564 C $1,568. D$1,600 E. $1,800