At long last you were able to afford a condo in the GTA. It cost $450,000 and you were able to come up with one third as a down payment and need to get a mortgage for the rest. A Toronto bank offers you a mortgage rate of 7% compounded semi-annually (with monthly payments) and gives you the option of a 20 year or 25 year amortization period. What's the difference in total interest paid over the life of the mortgage between the two alternatives?