Monthly repayment amount = (loan principal/repayment months)+(principal-accumulated amount of repaid principal) × monthly interest rate.

Repayment method: equal principal repayment;

Total repayment amount: 13 1006.25 yuan;

Total interest: 3 1006.25 yuan;

Monthly principal: 833.34 yuan;

Monthly interest of the first month: 5 12.50 yuan;

After that, the monthly interest payment will be reduced by 4.27 yuan;