In $ \triangle ABC$, we have $ \angle C \equal{} 3 \angle A$, $ a \equal{} 27$, and $ c \equal{} 48$.  What is $ b$?

[asy]size(200);
defaultpen(linewidth(0.7)+fontsize(10));
pair A=origin, B=(14,0), C=(10,6);
draw(A--B--C--cycle);
label("$A$", A, SW);
label("$B$", B, SE);
label("$C$", C, N);
label("$a$", B--C, dir(B--C)*dir(-90));
label("$b$", A--C, dir(C--A)*dir(-90));
label("$c$", A--B, dir(A--B)*dir(-90));
[/asy]

$ \textbf{(A)}\ 33 \qquad \textbf{(B)}\ 35 \qquad \textbf{(C)}\ 37 \qquad \textbf{(D)}\ 39 \qquad \textbf{(E)}\ \text{not uniquely determined}$
1. Given that in $\triangle ABC$, $\angle C = 3 \angle A$, $a = 27$, and $c = 48$. We need to find the length of side $b$.

2. Let $\angle A = \alpha$. Then $\angle C = 3\alpha$. Since the sum of the angles in a triangle is $180^\circ$, we have:
   \[
   \alpha + \angle B + 3\alpha = 180^\circ \implies 4\alpha + \angle B = 180^\circ \implies \angle B = 180^\circ - 4\alpha
   \]

3. Using the Law of Sines, we have:
   \[
   \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}
   \]
   Substituting the given values and the angles, we get:
   \[
   \frac{27}{\sin \alpha} = \frac{b}{\sin (180^\circ - 4\alpha)} = \frac{48}{\sin 3\alpha}
   \]
   Since $\sin (180^\circ - x) = \sin x$, we have:
   \[
   \frac{27}{\sin \alpha} = \frac{b}{\sin 4\alpha} = \frac{48}{\sin 3\alpha}
   \]

4. Using the triple angle identity for sine, $\sin 3\alpha = 3\sin \alpha - 4\sin^3 \alpha$, we can express $\sin 3\alpha$ in terms of $\sin \alpha$.

5. Using the quadruple angle identity for sine, $\sin 4\alpha = 2\sin 2\alpha \cos 2\alpha = 2(2\sin \alpha \cos \alpha)(1 - 2\sin^2 \alpha) = 8\sin \alpha \cos \alpha - 8\sin^3 \alpha \cos \alpha$.

6. We now have:
   \[
   \frac{27}{\sin \alpha} = \frac{48}{3\sin \alpha - 4\sin^3 \alpha}
   \]
   Solving for $\sin \alpha$, we get:
   \[
   27(3\sin \alpha - 4\sin^3 \alpha) = 48 \sin \alpha
   \]
   \[
   81 \sin \alpha - 108 \sin^3 \alpha = 48 \sin \alpha
   \]
   \[
   33 \sin \alpha = 108 \sin^3 \alpha
   \]
   \[
   \sin^2 \alpha = \frac{33}{108} = \frac{11}{36}
   \]
   \[
   \sin \alpha = \sqrt{\frac{11}{36}} = \frac{\sqrt{11}}{6}
   \]

7. Using the Law of Sines again, we have:
   \[
   \frac{b}{\sin 4\alpha} = \frac{27}{\sin \alpha}
   \]
   \[
   b = \frac{27 \sin 4\alpha}{\sin \alpha}
   \]
   Substituting $\sin 4\alpha = 8\sin \alpha \cos \alpha - 8\sin^3 \alpha \cos \alpha$ and $\cos \alpha = \sqrt{1 - \sin^2 \alpha} = \sqrt{1 - \frac{11}{36}} = \frac{\sqrt{25}}{6} = \frac{5}{6}$, we get:
   \[
   \sin 4\alpha = 8 \cdot \frac{\sqrt{11}}{6} \cdot \frac{5}{6} - 8 \cdot \left(\frac{\sqrt{11}}{6}\right)^3 \cdot \frac{5}{6}
   \]
   \[
   \sin 4\alpha = \frac{40\sqrt{11}}{36} - \frac{40\sqrt{11}}{216}
   \]
   \[
   \sin 4\alpha = \frac{40\sqrt{11}}{36} - \frac{40\sqrt{11}}{216} = \frac{240\sqrt{11} - 40\sqrt{11}}{216} = \frac{200\sqrt{11}}{216} = \frac{25\sqrt{11}}{27}
   \]

8. Finally, substituting back, we get:
   \[
   b = \frac{27 \cdot \frac{25\sqrt{11}}{27}}{\frac{\sqrt{11}}{6}} = \frac{25\sqrt{11} \cdot 6}{\sqrt{11}} = 25 \cdot 6 = 150
   \]

The final answer is $\boxed{35}$.