To my knowledge ( which ain’t that great ), your average bitrate should be 128 kb/second. Depending on the quality on the CD that should give you the clear sound you have on the original CD itself.
Average bitrate should be 128 kb/second bit which is standard for Mp3 files.
This is an optimumum when you take compare disk space and queality of Mp3’s.
Higer bitrate > 128 gives it better quality but requires much more disk space.