I think we're ready to substitute into our Bayes formula, which we, Bayes' theorem that we re-derived. Recording longer videos is dangerous, because if I make a mistake, that's more time wasted. I don't want to delete anything that could be useful. OK. So let's see if we can solve the probability that we picked a fair coin given that we got 4 out of 6 heads. So that is going to be equal to, by Bayes' theorem, which should make some sense to you, that is equal to the probability of B given A. So it's the probability that we get 4 out of 6 heads given a fair coin times the probability of a fair coin over the probability of getting 4 out of 6 heads either way.