7-15. You have 3 projects with the following cash flows: Year 0 1 Project 1 -150 2 3 4 20 40 60 80 0 0 -6500 60 80 -245 Project 2 -825 7000 Project 3 20 40 a. For which of these projects is the IRR rule reliable? b. Estimate the IRR for each project (to the nearest 1%). c. What is the NPV of each project if the cost of capital is 5%? 20%? 50%