First of all, it needs to calculate the loan amount of the car, that is,120,000 minus the down payment of 50,000 to get the loan amount of 70,000. Secondly, we need to determine the repayment period and interest rate. Assuming that the repayment period is three years and the interest rate is 5%, we can use the equal principal and interest method to calculate the monthly payment. According to the matching principal and interest method, the monthly repayment amount = loan amount × monthly interest rate ×( 1+ monthly interest rate) ÷(( 1+ monthly interest rate)-1).

According to this formula, we can calculate that the monthly repayment amount is 2 162.45 yuan. Therefore, this120,000 car has a down payment of 50,000, a repayment period of three years and an interest rate of 5%.