20 hours, so 2 extra 1.5 hours plus 8 hours at time and a half...
that makes it 30 hours (8+4(1.5)+8(2)) pay for one shift? Not a bad shift to be honest. The bigger issue, from what I've seen, is taking care of the patient's personal needs (bowel movements, feeding, turning, etc). The things that most EMS providers are neither trained in, nor willing to do in most cases.
Now don't forget to add start of shift, drive to the pickup, receive the patient, dropping the patient off, and end of shift activities, which is in reality all going to be at double time.
This is all assuming you aren't on 24 hour shifts (which goes at 40 hour work weeks regardless of the length of the shift).