The Chief Design Engineer for Colonial Warning Systems Wants to Know

Multiple Choice

The chief design engineer for Colonial Warning Systems wants to know the reliability of a two-lamp device intended to warn the operator of potential problems with a commercial steam kettle.One (either) lamp is to be lit if steam pressure drops below the desired level,and two (both) are to be lit if temperature drops below a desired level.His supplier estimates that a lamp has a failure rate of .2 per hour of operation,and a mean wear-out time of seven years with a standard deviation of eight months.What is the probability that a lamp will last at least until the expiration of the warranty,which is six years?

A) .9772
B) .9332
C) .8664
D) .8413
E) .4332