10 (10 marks) Consider the following cash flows and interest rates: 0 1 2 3 4 r = 2.5% r = 1.5% r = 1.9% r = 2.4% 5,000 5,000 5,000 5,000 a. Calculate the present value of these cash flows (at time 0). (5 marks) b. Calculate the future value of these cash flows (at time 4)