Answer
$30.3$ gallons
Work Step by Step
From the function
$C=21.6\sin \frac{2\pi }{365}\left(t+\frac{3978.5}{2\pi}\right)+30.3$,
the average daily fuel consumption is $30.3$ gallons.
The value of the average daily fuel consumption used is the vertical shift as this is the midway value of the daily consumption.
