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5a. Your parents are planning to buy a second house at the price of $500,000 with 20% down payment. While their bank offers a mortgage loan rate of 4% per annum. What is their monthly mortgage payment if they decide to pay off the mortgage in 30 years?

5b. You plan to save for your retirement. Suppose that you have 40 years to work and save money and another 30 years after you retire. If you need $6,000 at the beginning each month during retirement, how much do you need to save at the end of each month before retirement?