1-(1/5+2/15+1/4+1/4)=1-(12/60+8/60+15/60+15/60)=1-50/60=10/60=1/6还剩1/6未修完
甲效率:1/5*1/3=1/15乙效率:1/4*1/2=1/81-[1/5+1/4+2*(1/15+1/8)]=5/6
∑入党
