2006 Pascal Problem 21

In each row of the table, the sum of the first two numbers equals the third number. Also, in each column of the table, the sum of the first two numbers equals the third number. What is the sum of the nine numbers in the table?

\begin{array}{|c|c|c|}\hline m & 4 & m+4 \\ \hline 8 & n & 8+n \\ \hline m+8 & 4+n & 6 \\ \hline\end{array}

\textbf{(A)}\ 18\quad \textbf{(B)}\ 42\quad \textbf{(C)}\ -18\quad \textbf{(D)}\ -6\quad \textbf{(E)}\ 24

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.