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. 4 out of 6 heads. So 4 out of 6 heads given a fair coin, we figured that over here, that's 15 over 64. So this equals 15 over 64.