A manufacturer of light bulbs claims that its light bulbs ha

A manufacturer of light bulbs claims that its light bulbs have a mean life of 693 hours and a standard deviation of 110 hours. You purchased 140 of these bulbs and decided that you would purchase more if the mean life of your current sample exceeded 684 hours. What is the probability that you will not buy again from this manufacturer? (Give your answer correct to four decimal places.)