For these problems: (1) determine how many roots are possible and (2) graph the PW versus the interest rate to see whether multiple roots occur. If the root is a unique IRR, it is the project's rate of return. If there are multiple roots, then use an external investing rate of 12% and an external borrowing rate of 6%. Compute and use the MIRR as the project's rate of return. Problem 7A-4 Given the following cash flow, determine the rate of return on the project. Cash Flow Year 0 1 -$5,000 20,000 12,000 3,000