Well, we've already, so this means we're going to restrict our sample space to the essentially four equally likely outcomes that A has happened. So where A is true, I guess I could say. So there's one, two, three, four. And how many of them involve event B being true? Well, the only one of these four that involve event B being true is this one right over here where we've got our doubles. So there is a 1 1 4th probability that if we assume, given that we've gotten doubles, the probability that the four-sided die is a four. So this is a 1 1 4th probability.