The amount of time (in hours per week) a student utilizes a math-tutoring center roughly follows the normal distribution
$y=0.7979 e^{-(x-5.4)^{2} / 0.5}, \quad 4 \leq x \leq 7$
where $x$ is the number of hours.
(a) Use a graphing utility to graph the function.
(b) From the graph in part (a), estimate the average number of hours per week a student uses the tutoring center.