It has been found that times taken by people to complete a particular tax form follow a normal distribution with mean 100 minutes and standard deviation 30 minutes. A random sample of nine people who have completed this tax form was taken.

a) What is the probability that the sample mean time taken is more than two hours?

b) The probability is 0.20 that the sample mean time taken is less than how many minutes?

c) What is the probability that the sample mean time taken is less than 70 minutes?

d) What is the probability that a randomly chosen individual takes less than 70 minutes to complete this

particular tax form?