Ec=complement of E
E, F, G pairwise independent,P(G)>0
P(E∩F∩G)=0
To find: P(Ec∩Fc∣G)
P(A∣G)=P(G)P(A∩G)
Take A=Ec∩Fc
N=P(Ec∩Fc∩G)
Ec∩Fc∩G=G∖[(E∩G)∪(F∩G)]
N=P(G)−P(E∩G)−P(F∩G)+P(E∩F∩G)
P(E∩F∩G)=0⇒N=P(G)−P(E∩G)−P(F∩G)
P(E∩G)=P(E)P(G),P(F∩G)=P(F)P(G)
N=P(G)−P(E)P(G)−P(F)P(G)=P(G)[1−P(E)−P(F)]
Within G, E and F never occur together
P(Ec∩Fc∣G)=P(G)N=1−P(E)−P(F)
1−P(E)−P(F)=(1−P(E))−P(F)=P(Ec)−P(F)
⇒option (3)
P(Ec∩Fc∣G)=P(Ec)−P(F)