Help again please

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

Ineed in figuring out this problem.

The table shown below gives the approximate enrollment at the university of michigan every fifty years. how many more students were enrolled at the university of michigan in 1950 than in 1900?