A small trucking company has determined that on an annual basis the distance travelled per truck is normally distributed with a mean of 100.0 thousand kilometres and a standard deviation of 20.0 thousand kilometres.
(a) What proportion of trucks travel more than 150,000 km in the year?
(b) What distance will be travelled by 99% of trucks in the year?
(c) What is the probability that the average distance travelled in one year by the fleet of 8 trucks does not exceed 120,000 km?