The annual interest rates are 5. 145% and 5. 1% respectively.

I annual interest rate =5. 145%, monthly interest rate = annual interest rate/12=0.42875%.

Formula Monthly repayment amount = loan amount * monthly interest rate /[ 1-( 1+ monthly interest rate)-repayment months]

Monthly repayment amount = 690000 * 0.42875%/[1-(1+0.42875%)-360]

Monthly repayment amount = 3765.46 yuan

Total repayment amount = 1, 355,564.04 yuan.

Total interest = 665,564.04 yuan

2. Annual interest rate =5. 1%, monthly interest rate = annual interest rate/12=0.425%.

Formula Monthly repayment amount = loan amount * monthly interest rate /[ 1-( 1+ monthly interest rate)-repayment months]

Monthly repayment amount = 690000 * 0.425%/[1-(1+0.425%)-360]

Monthly repayment amount = 3746.35 yuan

Total repayment amount = 1, 348,687.24 yuan.

Total interest = 658,687.24 yuan

Third, calculate the interest difference under the two interest rates.

Monthly repayment amount difference = 19. 10 yuan.

Total repayment difference = 6876.80 yuan.

Total interest difference = 6,876.80 yuan

Results:

Under the hypothetical conditions, the difference between the monthly repayment amount under the two interest rates is 19. 10 yuan; The difference of the total repayment amount is 6876.80 yuan; The total interest difference is 6876.80 yuan.