posted by kevin .
The duration of time it takes General Motors to build a car is normally distributed with a mean of 31 hours and a standard deviation of 2 hours.
a) What is the probability that a single car, selected at random,
will take between 28 and 34 hours?
b) What is the probability that the mean of the times for a sample
of 25 cars will be between 28 and 34 hours?