2008 Pascal Problem 16

A circle has an area of M cm^2 and a circumference of N cm. If \dfrac{M}{N} = 20, what is the radius of the circle, in cm?

\textbf{(A)}\ 10\quad \textbf{(B)}\ 20\quad \textbf{(C)}\ 40\quad \textbf{(D)}\ \frac{1}{10}\quad \textbf{(E)}\ \frac{1}{20}

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Pascal contests here.