Isabelle purchased a house for $520,000. She paid 20% of the purchase price as a down payment and received a mortgage for the balance. The amortization period was for 25 years and she negotiated a fixed interest rate of 4.23% compounded semi-annually for a four-year term. She made mortgage payments at the end of every month. 1. What is the size of the monthly payment? (4 marks) 2. What is the principal balance at the end of the four-year term? (3 marks) 3. By how much time, expressed in years and months, will the amortization period shorten if Isabelle makes a lump-sum payment of $25,000, in addition to the monthly payment at the end of the four-year term of the mortgage? Assume that the mortgage contract does not charge her penalty for making this lump-sum payment. (4 marks)