Please explain #6. Answers are already provided but need to know the solution for #6 only. Thanks

Richard wants to obtain a $650,000 mortgage. The bank is quoting 7.25%, compounded semi-annually. He asks for a 25 year amortization with a three year fixed rate option. 1. What is the effective annual rate? (7.3814%) 2. What is the monthly payment? (\$4,653.47) 3. What is the total amount of interest paid on the mortgage? ($746,041.41) 4. How much interest is paid during the 2nd year of the mortgage? 5. What is the balance outstanding on the mortgage after the threeyear fixed rate term ends? ($618,610.65) 6. The banker suggests that Richard could shorten up the amortization by dividing his monthly payment in half and paying that amount every two weeks. What is the new amortization period (in both months \& years) using this method? (530.65 periods - of 2 weeks/period, which is equal to 20.4 years)