15. Calculate the present value of a reversion at the end of a 40-year useful life, assuming a 9% ROI. The site's value in 40 years will be $25,000. 16. If NOI is $10,000 and ROI is 9%, what is the present value of the property's income stream if the expected economic life is 25 years? 17. When Sam was born, his grandmother deposited $7,500 in a savings account bearing interest at 6% compounded monthly. The money was to pay for Sam's college costs and was to be given to him on his 17th birthday. How much did his grandmother estimate college would cost? 18. If Sam were to remove 1/4 of his money (see problem 17) on his 17th birthday, leave the remainder on deposit at 6% compounded monthly, and remove 1/3 of the remainder on this 18th birthday, 1/2 on his 19th birthday, and close the account on his 20th birthday, how much would he have for his 4 years of college? 19. When he reached 17, Sam estimated his college costs would be $30,000. What should his grandmother have deposited assuming the same interest characteristics? 20. You are planning to purchase a car upon graduation in three years. The price of the car today is $5,000 and is increasing at the rate of 8% per year (compounded). How much money should you deposit each month, starting one month from now, at an annual rate of 6% compounded monthly, so that you will be able to purchase the car in 3 years