The monthly repayment amount is 4000 yuan.

Assuming that the annual interest rate is x%, the repayment period of the loan is calculated by matching the principal and interest.

1. Calculate the monthly interest rate: convert the annual interest rate into the monthly interest rate, that is, x/ 12%.

2. Calculation of loan repayment period: According to the loan amount, monthly repayment amount and monthly interest rate, the repayment period is calculated by using the equal principal and interest repayment formula. The formula is as follows:

n =-log（ 1-（P * r）/M）/log（ 1+r）

Where n is the repayment period (month), p is the loan amount, r is the monthly interest rate and m is the monthly repayment amount.

3. Convert the calculated repayment period into years: divide the repayment period by 12.

Summary:

According to the information given, it is impossible to determine the specific annual interest rate and loan repayment period. Only according to the input data, the number of years of loan repayment period can be calculated.

Extended data:

-In practice, borrowers usually need to consider factors such as interest rate, loan term and repayment method to choose the most suitable mortgage loan scheme.

-The choice of loan repayment period can be weighed according to personal economic situation, repayment ability and capital liquidity.

-Note that the calculation in this answer is only for demonstration. Relevant financial institutions or professional consultants should be consulted for accurate loan calculation and suggestions.