From looking at previous cell phone bills, a student notes that her calls per month follow an approximately normal distribution with a mean of 172 minutes and a standard deviation of 26 minutes.

a) Sketch a graph of the density function, indicating the values for the mean and standard deviation. (You do not need to determine the values of f(x) for the y­axis.)
b) The student is considering using a calling plan that allows 200 minutes per month free. Assuming the distribution from part (a) continues, what is the probability that the student will exceed 200 minutes in a month?