Answer to Question #79585 in Statistics and Probability for mishen ukr

Question

the lifetime of a car batteries is normally distributed with mean 1 year and standard deviation 1.5 months
a)calculate the probabilty that a randomly selected car battery will last 10 to 11 months
b)calculate the minimum lifetime of the 30% longest lasting car batteries
c) by improing the quality of the car batteries, the lifetime is to be increased such that only 2.5% of the car batteries will fail before 10 months.Find the new mean lifetime of the car batteries, Assume the standard deviation remains unchanged,