[Xelent]

The minimum raise would actually be to $18, not $20.

Making it $10 to go is an $8 raise. So you can re-raise $8 more to $18.

As far as your question is concerned, I am not sure, however I do not believe the 3rd player is allowed to raise because the 2nd players all in was 16 and not 18. I could be wrong though.