Assume that a population is normally distributed with a mean of 100 and a standard deviation of 15

Assume that a population is normally distributed with a mean of 100 and a standard deviation of 15. Would it be unusual for the mean of a sample of 3 to be 115 or more? Why or why not?

What if the size for each sample were increased to 20? Would a sample mean of 115 or more be considered unusual? Why or why not?

What about if we have:

The mean of a sample of 20 is 105 or more?  Is this an unusual event looking at this information?  Why is the Central Limit Theorem used?  Explain!