Answer:

So we can express the radius in terms of the hours elapsed like this:

And the reason of this is because each hour the radius increase 6.5 inches, and if we replace in the formula of area we got:

And this function would represent the area of the circle as function of the hours elapsed,
Explanation:
For this case we know the radius of a circle given
and we also know the incresing rate for the radius:

And we want to express the are of the circle A as a function of h = the number of hours elapsed.
We know that the area of a circle is given by:

So we can express the radius in terms of the hours elapsed like this:

And the reason of this is because each hour the radius increase 6.5 inches, and if we replace in the formula of area we got:

And this function would represent the area of the circle as function of the hours elapsed,