On June 15, Kersee Company sold merchandise on account to Eng Co. for $1,000, terms 2/10, n/30. On June 20, Eng Co. returns merchandise worth $300 to Kersee Company. On June 24, payment is received from Eng Co. for the balance due. What is the amount of cash received on June 24?
a) $700.
b) $680.
c) $686.
d) None of the answer choices are correct.