Would anyone be able to assist me with this....homework problem?

"Consider a channel whose transmitter noise = its receiver noise 1microWatt. In addition, let channel noise accumlate at 50nW/km.
Ignore its attenuation. Let the signal's transmit power = 100mW and
let the signal attenuate at -6dB/km. If we require the receiver's
SNR dB, what is the maximum line length?"

I'm not quite sure how to solve this. I know the SNR is the ratio of the power of the signal at the receiver to the noise at the receiver. But how exactly do I incorporate the noise into this equation given that the units for noise are not in dB? Any help is appreciated. Thanks.

Vincent

"Consider a channel whose transmitter noise = its receiver noise 1microWatt. In addition, let channel noise accumlate at 50nW/km.

I'm not quite sure how to solve this. I know the SNR is the ratio of the power of the signal at the receiver to the noise at the receiver. But how exactly do I incorporate the noise into this equation given that the units for noise are not in dB? Any help is appreciated. Thanks.

Vincent