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 warranty period for a lamp would give a probability of .9987 that it would not require warranty service?

A) 5 years
B) 5.67 years
C) 6.33 years
D) 7 years
E) 9 years