hello i just need explain how answer here is A asap plz thank you

4) 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 28 , it paid the full amount due. The amount of the cash paid on July 28 equals: A) $200. B) $1,564. C) $1,568. D) $1,600. E) $1,800