4. Each year a certain amount of money is deposited in an account which pays an
annual interest rate of r so that at the end of each year the balance in the account is
multiplied by a growth factor of x = 1 + r. $1,000 is deposited at the start of the first
year, an additional $300 is deposited at the start of the next year, and $500 at the
start of the following year.
