The mean useful life of car batteries is 50 months. They have a standard deviation of 2. Assume the useful life of batteries is normally distributed. a. Calculate the percent of batteries with a useful life of less than 46 months. (Round your answer to the nearest hundredth percent.) b. Calculate the percent of batteries that will last longer than 56 months. (Round your answer to the nearest hundredth percent.) Percent of batteries Percent of batteries