11. In the following circuit, the four relays work independently of one another. Each label records the probability that one of the relays is closed (so, for example, the probability that the second relay in the middle branch is closed is p3 = 0.3).
p1 = 0.1
p2 = 0.2
p3 = 0.3
p4 = 0.4
(a) Find the probability that current does not pass through this circuit.
(b) Find the probability that current does pass through.
(c) Find the probability that current passes through, given that the second relay in the middle branch is open.