A P/OM Student Has Purchased a Four-Function Calculator for Use

Multiple Choice

A P/OM student has purchased a four-function calculator for use during exams.This calculator is perfectly reliable except for two parts: its microchip,which has a failure rate of one in every twenty hours of operation; and its battery,which has a failure rate of one in every ten hours of operation.Also,on average the battery will fail in five hours,with a standard deviation of 30 minutes.Assuming that a new battery has just been installed and the student brings one spare battery with him,what is the probability that the calculator will perform reliably during a one-hour exam?

A) 0.89775
B) 0.9405
C) 0.987525
D) 0.99
E) 0.9975