计算器的话怎么算PBP和DPB啊？

问题如下：

Given the following cash flows for a capital project, calculate its payback period and discounted payback period. The required rate of return is 8 percent.

The discounted payback period is:

选项：

0.16 years longer than the payback period.

0.51 years longer than the payback period.

1.01 years longer than the payback period.

解释：

C is correct.

As the table shows, the cumulative cash flow offsets the initial investment in exactly three years. The payback period is 3.00 years. The discounted payback period is between four and five years. The discounted payback period is 4 years plus 24.09/3,402.92= 0.007 of the fifth year cash flow, or 4.007 = 4.01 years. The discounted payback period is 4.01 − 3.00 = 1.01 years longer than the payback period.