It is known that an investment of 100 will increase to 150 at the end of 5 years. Find the sum of the present values of three payments of 4649 each which will occur at the end of 5,10 and 15 years. Assume a constant annual effective interest rate. (nearest cent) Answer: The two sets of grandparents for a grandchild on their 10nth birthday wish to invest enough money to pay $20,000 each year for four years toward college costs starting on their grandchild's 18th birthday. Grandparents A agree to pay the first two payments, while grandparents B agree to pay the last two payments. If the effective interest rate is 6% annual compound interest, find the difference between the contributions of grandparents A and B