Right when I put my hand into the bag and I pick out a coin, there's a 5 in 10 chance, or 5 in 15 chance, right, there are 15 total coins, that I pick a fair coin. So 5 in 15, that's the same thing as 1 third, that I pick a fair coin. And then there's a 2 thirds chance that I pick a unfair coin. Now if I pick a fair coin, given that I have a fair coin, what is the probability given the fair coin, what is the probability that I get 4 out of 6 heads? Well once again, let's think about the previous several videos. What's the probability of getting any one particular combination of 4 out of 6 heads? So for example, it could be heads, tails, heads, tails, heads, heads.