Vince Trucking Company determined that, on an annual basis, the distance traveled per truck is normally distributed with a mean of 50.0 thousand miles and a standard deviation of 12 thousand miles. If a sample of 16 trucks is selected,

1. What is the probability that the average distance traveled is less than 45.0 thousand miles in a year?
2. What is the probability that the average distance traveled is between 44.0 and 48.0 thousand miles in the year?
3. What assumption must be made in order to solve (a) and (b)?
4. If a random sample of 64 trucks is selected, there is a 95% chance that the sample mean will be below how many miles?