4. A young man wants to retire at the age of 40 (in 15 years' time). He estimates that he will need to have R1.5m to buy a property of his own. He intends to make equal monthly payments into a bank account on which he can earn 8% interest compounded monthly. Required (Show all steps): a) What amount must he pay monthly to achieve his objective in 15 years' time? The first payment is to be made at the end of the first month. b) Instead of making equal monthly payments, he wants to make one single sum payment today, investing it at 8% interest p.a. What should this single sum be