Three analog signals, having bandwidths $1200 \mathrm{~Hz}$, $600 \mathrm{~Hz}$ and $600 \mathrm{~Hz}$, are sampled at their respective Nyquist rates, encoded with $12$ bit words, and time division multiplexed. The bit rate for the multiplexed signal is
- $115.2 \; \mathrm{kbps}$
- $28.8 \; \mathrm{kbps}$
- $57.6 \; \mathrm{kbps}$
- $38.4 \; \mathrm{kbps}$