In the summer the activity level of a certain type of lizard varies according to the time of day. A biologist has determined that the activity level is given by the function below, where $t$ is the number of hours after 12 noon. When is the activity level highest? When is it lowest?
$a(t) = 0.008t^3 - 0.287t^2 + 2.305t + 2$
Choose the correct answer below.
A. The highest level of activity occurs at 5:06 P.M., and the lowest level of activity occurs at 6:49 A.M.
B. The highest level of activity occurs at 4:06 P.M., and the lowest level of activity occurs at 5:49 A.M.
C. The highest level of activity occurs at 4:06 P.M., and the lowest level of activity occurs at 6:49 A.M.
D. The highest level of activity occurs at 5:06 P.M., and the lowest level of activity occurs at 5:49 A.M.