Which of the following statements is CORRECT?

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a$.$ The higher the WACC, the shorter the discounted payback period.

b$.$ The MIRR method assumes that cash flows are reinvested at the crossover rate.

c$.$ The IRR method can never be subject to the multiple IRR problem, while the MIRR method can be$.$

d$.$ The MIRR and NPV decision criteria can never conflict.

e$.$ One reason some people prefer the MIRR to the regular IRR is that the MIRR is based on a generally more reasonable reinvestment rate assumption.