Perry decides to wait until his niece starts kindergarten to start her college fund. If he is depositing $100 per month into an account that pays 10%, how much will there be for her in 13 years?

Martin wants to accumulate $50,000 to make a down payment on a house. He currently has $15,000 saved toward this goal. He can invest $500 at the end of every month for the next four years. What interest rate, compounded monthly, will allow Martin to achieve his goal?