150000 yuan loan is paid off in one year, and the head office needs to pay back 153420 yuan. The loan interest is calculated by monthly compound interest, with the monthly interest rate of 0. 19%/ 12, and one year 12 months. According to the benchmark interest rate, the annual interest is: conventional algorithm: interest = principal * interest rate, and the monthly interest of a loan 1500 is: 1500.