The reinvestment assumption of the IRR method may not be valid in an engineering economy study. For instance, if a firm’s MARR is 20% per year and the IRR for a project is 42.4%,it may not be possible for the firm to reinvest net cash proceeds from the project at much more than 20%.This situation,coupled with the computational demands and possible multiple interest rates associated with the IRRmethod,has given rise to other rate of return methods that can remedy some of these weaknesses.