10) A thirty-year mortgage with no early repayment option is repaid with level monthly payments. The interest rate on the mortgage is 6.8% nominal convert- ible monthly Calculate the Macaulay duration on the mortgage at the equiva- lent annual effective interest rate. 10) A thirty-year mortgage with no early repayment option is repaid with level monthly payments. The interest rate on the mortgage is 6.8% nominal convert- ible monthly Calculate the Macaulay duration on the mortgage at the equiva- lent annual effective interest rate