In the rectangular parallelepiped shown, $AB=3$, $BC=1$, and $CG=2$. Point $M$ is the midpoint of $\overline{FG}$. What is the volume of the rectangular pyramid with base $BCHE$ and apex $M$? $\textbf{(A) }1 \qquad$ $ \textbf{(B) }\frac{4}{3} \qquad$ $ \textbf{(C) }\frac{3}{2} \qquad$ $ \textbf{(D) }\frac{5}{3} \qquad$ $ \textbf{(E) }2 \qquad$