When we put our hand in the bag and we take one of the coins out, there's some probability that we get an unfair coin. And three of the four coins are unfair. So there's a 3 4 probability that we get an unfair coin. And then there is only one out of the four coins that's fair. So there was a 1 4 probability that I get a fair coin. Now, given that I have unfair, let's remind ourselves. An unfair coin has a 45% chance of coming up tails.