You expect your newly born child to attend college in 18 years. You have $12,000 to set aside (or that purpose. You also expect that the total cost of college education to be $100,000 by that time. Calculate the interest rate at which you have to invest today to achieve your goal. How long does it take to double your money at 9 % interest rate? How long does it take to triple your money at 9% interest rate?