AMC 8 1987 Problem 12

What fraction of the large $12$ by $18$ rectangular region is shaded?

$\text{(A)}\ \frac{1}{108} \text{(B)}\ \frac{1}{18} \text{(C)}\ \frac{1}{12} \text{(D)}\ \frac29 \text{(E)}\ \frac13$