单项选择题
A.IRR<ic B.IRR<0 C.IRR≥ic D.IRR>0
A、①② B、②③ C、①③ D、①②③
A.zn=b(2.5-0.4lnb) B、σz/σcz≤0.2 C.σz/σcz≤0.1 D.ΔSn≤0.025∑ΔS1