问题如下：
An investment will provide cash flows to investors as folloing pattern
$20 in Year 1, -$10 in Year 2, $10 in Year 3, and then send back $100 principal at the end of Year 4.
Assume the discount rate is 8%. Calculate the present value of the investment:
选项：
A.$91.39.
B.$108.29.
C.$135.58.
解释：
A is correct.
CF0 = 0; CF1 = 20; CF2 = -10; CF3 =10; CF4 = 100; I/Y = 8;
NPV= $91.39.
您好！这个答案是参照计算器的哪个模式按出来的呢？是现金流模式还是净现值模式？我发现答案是按照两个模式结合的，我按照现金流模式将各期现金流输入计算器之后，I/Y不知道怎么输入？我自己计算是按照笨办法，一个个算现值后加总在一起的，但是速度较慢，所以求更快的计算方法。
