The mean time to download the homepage of the University of PEI is 0.8 second. Suppose that the download time is normally distributed with a standard deviation of 0.2 second. If you select a random sample of 25 download times,

1) What is the probability that the sample mean is less than 0.75 second?

2) What is the probability that the sample mean is between 0.70 and 0.90 second?

3) What is the probability that the sample mean is less than 0.70 or more than 0.90 second?

4) The probability is 0.8 that the sample mean is between what two values symmetrically distributed around the mean?