 As before, I have a bunch of study questions for you. They are mostly related to these concepts of free energy and everything. Walk through them, they're present on the canvas side too if you want that. And in particular, I know that this can be difficult, but you need to start having at least some sort of gut feeling for what all these numbers are and you need to know what they represent. If you found it difficult to follow that last derivation that I made for the hydrogen bond, that's not surprising. In that case, sit through and review all the components of this lecture once again. And then take your time. Let this take an hour. And sit through and do the last question again and think about what are the values of these signs. It's not hard, but nobody says that you're expected to solve this in 30 seconds the first time. Trust your equations and let they help you through it. See you for lecture four.