23. Given the seven-year payback, the worst case is that the payback occurs at the end of the seventh
year. Thus, the worst-case:
The best case has infinite cash flows beyond the payback point. Thus, the best-case NPV is infinite.
24. The equation for the IRR of the project is:
Using Descartes rule of signs, from looking at the cash flows we know there are four IRRs for this
We would accept the project when the NPV is greater than zero. See for yourself that the NPV is
25. a. Here the cash inflows of the project go on forever, which is a perpetuity. Unlike ordinary
perpetuity cash flows, the cash flows here grow at a constant rate forever, which is a growing
PV of cash inflows = C1/(R – g)
NPV is the PV of the inflows minus the PV of the outflows, so the NPV is:
The NPV is positive, so we would accept the project.
b. Here we want to know the minimum growth rate in cash flows necessary to accept the project.
Solving for g, we get: