Buffon Electronics Company issues a 2,000,000, 10%, 20-year mortgage note on January 1. The terms provide for annual installment payments, exclusive of real estate taxes and insurance, of 234,920. After the first installment payment, the principal balance is

a. 2,000,000 b. 1,965,080 c. 1,983,448 d. 1,558,250

The answer is (c) and I cannot understand why the answer is not (b) but (c)...