Circadian Rhythms Everybody's blood pressure
varies over the course of the day. In a certain individual
the resting diastolic blood pressure at time $t$ is given by
$B(t)=80+7 \sin (\pi t / 12),$ where $t$ is measured in hours
since midnight and $B(t)$ in mmHg (millimeters of mercury).
Find this person's resting diastolic blood pressure at
(a) $6 : 00$ A.M. (b) $10 : 30$ A.M. $(\mathbf{c})$ Noon (d) $8 : 00$ P.M.