Clean up and transcribe English audio quickly and accuratelly

I need to transcribe bad quality intermittent noise meeting audio with 3 people.
You should be able to clean up the audio as it is important to hear what was said, if not every word then most of them. The audio is in mp3 format so it might not be possible to recover everything, but every effort should be made.
Initially I would like to do 20 minutes, for which I would like to get results in 12 hours,
but if you can produce quality results quickly then I would be glad to offer more work afterwards.