The water level of a certain body of water is changing at a rate of $W(t)=\dfrac12\cos\left(3-\dfrac t2\right)$ inches per hour, where $t$ represents hours since $12$ a.m.
(A.) Write the integral that represents the number of inches that the water level changes from $6$ a.m. to noon.
(B.) What is the average daily number of inches that the water level changes for this lake?
(A.) So for this part, I'm pretty sure the integral would be $\displaystyle\int_6^{12}W(t)\,\mathrm dt$. Is this correct?
(B.) This is what I'm most confused about. Am I supposed to use average values, like maybe $$2\left[\frac 1{12-0}\int_0^{12}W(t)\right]\quad ?$$