Don't know how to solve

The amount of pollutants that are found in waterways near large cities is normally distributed with mean 9 ppm and standard deviation 1.4 ppm. 36 randomly selected large cities are studied. Round all answers to 4 decimal places where possible. (a) What is the distribution of X? X ~ NC (b) What is the distribution of a? I ~ N( (c) What is the probability that one randomly selected city's waterway will have less than 8 ppm pollutants? (d) For the 36 cities, find the probability that the average amount of pollutants is less than 8 ppm