3) Professor G wants to have $800,000 in his retirement account when he retires in 5 years. He earns 6.6% on his investments guaranteed. How much must he invest at the beginning of each month if he now already has $440,000 already saved up? 4) Professor G wants to take out a mortgage for $250,000. He has a choice of taking a 20- year 3.6% mortgage or a 30-year 4.2% mortgage. How much interest will he save if he chooses the 20 year mortgage? Assume payments are made at the end of each month