问题如下：
When assembling the cash flows to calculate an NPV or IRR, the project’s after-tax interest expenses should be subtracted from the cash flows for:
选项：
A.the IRR calculation, but not the NPV calculation.
B.both the NPV calculation and the IRR calculation.
C.neither the NPV calculation nor the IRR calculation.
解释：
C is correct.
Financing costs are not subtracted from the cash flows for either the NPV or the IRR. The effects of financing costs are captured in the discount rate used.
老师请问，看到有助教的回复是“其实这里的不考虑就是不踢除的意思，因为利息费用是一项成本（现金流的递减项），如果我们k考虑它，就要从现金流中减掉。但是财务成本我们是考虑在分母上，分子现金流就不再考虑了（也就是不再扣减了）”。那么沉没成本在计算cash flow也是ignore的，那沉没成本是在哪里被ignore呢？分子还是分母呢？
