3. A system is composed of 6 subsystems A, B, C , D. E and F as indicated in fig. 1. If all of them function independently with probabilities P(A)=.9, P(B) =.8, P(C) = .7, P(D) = .5; P(E) = .6 and P(F) = .4 what is probability of successful system operation? C B D E F