The life of a semiconductor laser at a constant power is normally distributed with a mean of 3500 hours and standard deviation of 400 hours. a. What is the probability that a laser fails before 3000 hours? b. What is the life in hours that 95% of the lasers exceed? c. If there are two lasers used in a product, and they are assumed to fail independently, what is the probability that both of them are still operating after 3500 hours?