问题如下图：
选项：
A. 
B. 
C. 
解释：
这个题目中正数的现金流默认是流出还是流入啊？
我在做题的时候，send back 100，按照现金流入，不知道该正数还是负数。
$108.29. $135.58. A is correct. CF0 = 0; CF1 = 20; CF2 = -10; CF3 =10; CF4 = 100; I/Y = 8; NPV= $91.39.请问Npv的计算怎的按计算器
$108.29. $135.58. A is correct. CF0 = 0; CF1 = 20; CF2 = -10; CF3 =10; CF4 = 100; I/Y = 8; NPV= $91.39.请问NPV的知识点在哪里出现的？
NO.PZ2015120604000008 $108.29. $135.58. A is correct. CF0 = 0; CF1 = 20; CF2 = -10; CF3 =10; CF4 = 100; I/Y = 8; NPV= $91.39. 如何判断现金流从第几期开始
NO.PZ2015120604000008 20/（1+8%）+ -10/（1+8%）^2 +10/(1+8%)^3+100/(1+8%)^4 因为每期的现金流不相等 所以不能这样计算是吗？
$108.29. $135.58. A is correct. CF0 = 0; CF1 = 20; CF2 = -10; CF3 =10; CF4 = 100; I/Y = 8; NPV= $91.39.请问这是R6里面的哪个知识点呢？
