Ineed writing a quadratic equation for this graph

How do i do this activity, is appreciated

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?

What is the solution to the equation? k/6.4=8.7 2.3 5.568 15.1 55.68