Assume that the burning times of electric light bulbs approximate a normal curve with a mean of 1200 hours and a standard deviation of 120 hours. If a large number of new lights are installed at the same time (possibly along a newly opened freeway), at what time will(a) 1 percent fail?(b) 50 percent fail?(c) 95 percent fail?(d) If a new inspection procedure eliminates the weakest 8 percent of all lights before they are marketed, the manufacturer can safely offer customers a moneyback guarantee on all lights that fail before _____ hours of burning time