On April 30, 2021, one year before maturity, a Corporation retired $500,000 of 6% bonds payable at 102. The book value of the bonds on April 30 was $492,500. Bond interest was last paid on April 30, 2021. What is the gain or loss on the retirement of the bonds?

A. $17,500 loss B. $7,500 loss C. $17,500 gain D. $7,500 gain