2000 Pascal Problem 12

In the diagram, every number beginning at 30 equals twice the sum of the two numbers to its immediate left. The value of c is

\begin{array}{|c|c|c|c|c|}\hline 10 & a & 30 & b & c \\ \hline\end{array}

\textbf{(A)}\ 50\quad \textbf{(B)}\ 70\quad \textbf{(C)}\ 80\quad \textbf{(D)}\ 100\quad \textbf{(E)}\ 200

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.