At the age of 30 you decide to start saving money. At first you can only afford to deposit $200 per month. However, at the age of 38 you are able to deposit $300 per month. Then at the age of 45 you raise your monthly deposit again to $500 per month. Finally at the age of 50 you get promoted to president of the company and are able to deposit $2000 per month into the account.
Assuming your account is earning (prime interest rate + 4%) in interest, compounded monthly, how much do you have in your account at the age of 70? Hint: Treat each time that you change the deposit amount as a separate annuity, and compute the future value (FV) on each annuity seperately. Assume that each annuity earns compound interest during the time it is not receiving deposits.