I am having a little trouble with this problem. Any help would be greatly appreciated.

The daily consumption $\displaystyle C$ (in gallons) of diesel fuel on a farm is modeled by

$\displaystyle C=30.3+21.6sin(\frac{2PIt}{365}+10.9)$

(PI=3.14....)

where $\displaystyle t$ is the time in days, with $\displaystyle t=1$ corresponding to January 1.

a)What is the period of the model? Is it what you expected? explain

so I know the $\displaystyle period=\frac{2PI}{\frac{2PIt}{365}}$ but then how do I simplify that?

b) What is the average daily fuel consumption? Which term of the model did you use? explain.

c)use a graphing utility to graph the model. Use the graph to approximate the time of the year when consumption exceeds 40 gallons per day.

I am confused on the rest, please help. Thank you.