If $y$ varies inversely as the cube of $x$ and $y = 64$, when $x=4$, then what is the value of $y$ when $x =3$ ?

Question

$\begin{array}{1 1} (a)\; 4096 \times 9 \\ (b)\; \frac{4096}{9} \\ (c)\; \frac{9}{4096} \\ (d)\; \text{none of the above} \end{array}$