Let’s see you’re still using the slightly older mastering, so you will still be using RMS Normalize (later Audacity versions have a built-in one called Loudness Normalization).
This is the hum remover I’m using.
de-hum.ny (2.11 KB)
It shows up in Audacity as “Hum Remover.” I posted the settings.
Noise Reduction is in two passes. Drag-select some typical noise. Effect > Noise Reduction > Profile.
Then select the whole chapter and Effect> Noise Reduction at the settings I posted > OK.
Analyze > ACX Check. Either one works. The longer one has more information, but you only need those three readings.
Which Audacity and which Mac?
Koz