A video transmission system transmits $625$ picture frames per second. Each frame consists of a $400 \times 400$ pixel grid with $64$ intensity levels per pixel. The data rate of the system is
- $16 \; \mathrm{Mbps}$
- $100 \; \mathrm{Mbps}$
- $600 \; \mathrm{Mbps}$
- $6.4 \; \mathrm{Gbps}$