If $\frac{2a}{3b} = \frac{3c}{4d}$, which of the following is equal to $bc$ ?

Question

$\begin{array}{1 1} (a)\; \frac{9ad}{8} \\ (b)\; \frac{8ad}{9} \\ (c)\; \frac{8a}{9d} \\ (d)\; \frac{9a}{8d} \end{array}$