Scientists sometimes use the formula
$f(t)=a \sin (b t+c)+d$
to simulate temperature variations during the day, with time $t$ in hours, temperature $f(t)$ in $^{\circ} \mathbf{C},$ and $t=\mathbf{0}$ corresponding to midnight. Assume that $f(t)$ is decreasing at midnight.
A. Determine values of $a, b, c,$ and $d$ that int the Information.
B. Sketch the graph of $f$ for $0 \leq t \leq 24$
The temperature varies between $10^{\circ} \mathrm{C}$ and $30^{\circ} \mathrm{C}$, and the average temperature of $20^{\circ} \mathrm{C}$ first occurs at $9 \mathrm{A} . \mathrm{M}$.