Using Descartes rule of signs, from looking at the cash flows we know there are four IRRs for this project. Even with most computer spreadsheets, we have to do some trial and error. From trial and error, IRRs of 25 percent, 33.33 percent, 42.86 percent, and 66.67 percent are found. We would accept the project when the NPV is greater than zero. See for yourself that the NPV is greater than zero for required returns between 25 percent and 33.33 percent or between 42.86 percent and 66.67 percent.