In Puzzle 5, you should exchange 2 tiles against a rooster. Exchanging 2 against a rooster will make it much more likely that the rooster will also exchange tiles, which is the best that you can hope more with this opening rack, as any E, I, N, O, R, or several other 2 tile combinations will give you 50 point plays next turn. Since roosters exchange so often because they expect you to have a bingo rack, you can take advantage of this by making a small equity sacrifice in an attempt to trick the rooster.