How to calculate the installment interest of China Merchants Bank

The number of issues of issued bills is at least 2 and at most 24; The shortest arrears period is 2 periods, and the longest is 12 periods; The first stage lasts for one month. The bill installment fee is included in the monthly installment repayment bill, and the installment fee = total installment amount × installment rate. The rate for Phase 2 is 1.0%/ period; The third installment rate is 0.9%/ period; The interest rate for the sixth period is 0.75%/ period; 10 installment rate is 0.7%/ period; 12 installment rate is 0.66%/ period; 18 installment rate is 0.68%/ period; The rate for the 24th installment is 0.68%/ installment.