Which is not a line of symmetry'

You can find the constant of proportionality by finding the ratio of

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?

How to do this , and can some one explain