a coaxial cable can carry signals in the range 50mhz to 450mhz. The bandwidth of cable is divided into a numbe of sub-channels each occupying with the guard band, 40mhz of bandwidth. In each channel the guard band takes up 4 mhz (i.e. 2mhz either side of the sub channel, making a total of 4mhz between adjacent sub channels). If the signal to noise ratio in each sub channel is 30dB. calculate the maximum capacity of each sub-channel and hence the maximuim total capacity of the cable.