What are the amplitude, period, and midline of f(x) = -4 cos(2x-n) + 3?

Me find the measure to side a and the process to solve the problem you appreciate it : )

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?

When y’all answer can y’all explain too !