4) ABC Corporation makes electrical watches. The lifetime (period during which a watch does not need major repair) of an electronic watch manufactured by this corporation has a normal distribution with a mean of 55 months and a standard deviation of 7 months. a) What is the probability that a randomly selected electronic watch of this kind has lifetime at least 50 months? b) What percent of watches of this kind will have lifetime between 50 and 65 months? c) Any watch that needs a major repair during the warranty period will be replaced free by the company. What should be the warranty period if the company does not want to replace more than 5% of the watches?