<P>我现在正在复习corporate finance这块内容，其中看了payback period的内容以后再来做题，发现有点被弄糊涂了，这道题是这样的，A company is considering the purchase of a copier that cost $5000, Assume a required rate of return 10% and the following cash flow schedule:Year1,$3000, Year2,$2000, Year3,$2000. What is the project 's payback period? The answer is two years.书上说在计算payback 的时候，公式中的分子是用的cumulative net cash flow,而这个地方在计算payback时直接用-5000+3000+2000=0就得出了payback period is two year. How can I comprehend it? 请各位仁兄给我一点指导，谢谢。</P>