In 1960, John Smith, Jr. took out a constant payment, fully amortizing mortgage in the amount of $90,000. The loan was for 20 years, and carried an annual interest rate of 3.5%. Showing your answer to the nearest whole cent, how much was the combined monthly payment of principal and interest on this mortgage? (Note: do not worry about the payment amount for the very last month; I am referring here to the payment amount that applies to each of the other months.)