AHSME 1950 Problem 2

Let $R=gS-4$. When $S=8$, $R=16$. When $S=10$, $R$ is equal to: $\textbf{(A)}\ 11 \textbf{(B)}\ 14 \textbf{(C)}\ 20 \textbf{(D)}\ 21 \textbf{(E)}\ \text{None of these}$