1. The problem statement, all variables and given/known data 2. Relevant equations The given channel transfer function and PSDs. Note that the capital Pi symbol in the PSD of the message symbolizes the rectangle function so Sm(f) = 8rect(f/8000) 3. The attempt at a solution From my understanding, channel noise is not filtered at this point since it's additive to the signal in the channel. I get an answer of B = 0.000164 Hz, which doesn't seem reasonable. Including the negative frequencies, a bandwidth of 2B = 0.000328 Hz still doesn't make much sense to me.