I totally get what you are asking, but I would also suggest you are approaching the equation initially from the wrong direction. The starting point should be "how many passengers do I need to move?".
If you want to move 36, then a 139/189/175 will need three trips. An S92/225 would only require two and therefore wins
If you want to move 32, then the financially equation swings in favour of the 189/175.
The numbers to answer your real question are obviously known by some, but here isn't where you will find them as they are commercially sensitive
For "public domain" info, do a search for Conklin & de Decker, then get hold of a credit card
