A.30000/[(42450+77550)/2]=0.5次 B.30000/42450=0.707次 C.30000/(42450+77550)=0.25次 D.30000/77550=0.387次
A.(30000-22000)/30000×100%=26.7% B.(30000-22000-500)/30000×100%=25% C.(35100-5100-22000)/35100×100%=22.8% D.(35100-5100-22000-500)/35100×100%=21.4%