4. A data communications line is fed with input signal whose power is 0.6 watt and the output noise is measured as 20 uwatt. [15 points) a) Calculate the output signal-to-noise ratio (in dB) if the line loss is 20 dB. (Assume Line Loss (dB) = 10 * logidinput signal power/output signal power) b) What is the capacity of this line when the frequency band is 2500 KHz? c) If the attenuation rate of this data comm. line is 8 dB/Km, and the minimum output signal is 0.008 watt, how long can this line be before requiring a repeater (a device to amplify the signal)