And we see that right over here. The six-sided die has to be a four as well in order for this to be doubles because we're assuming where it's given that B, we're given of event B. We're restricting our sample space with event B. What is the probability of B given A? The probability that the four-sided die is four given that Erica rolls doubles. So let's just think about that a little bit. So the probability of B given A.