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Flight Pattern

A small, experimental plane has three engines, one of which is redundant. That
is, as long as two of the engines are working, the plane will stay in the air.
Over the course of a typical flight, there is a 1/3 chance that engine one will
fail. There is a 75% probability that engine two will work. The third engine
works only half the time. What is the probability that the plane will crash in
any given flight?

(A) 7/12
(B) 1/4
(C) 1/2
(D) 7/24
(E) 17/24