So basically we have to look at three individual cases when we have zero boys, when we have one boy, and when we have two boys, okay? And then we find the probabilities of these events and we sum them up because they are mutually exclusive. So let's begin with zero boys. So zero boys is the same thing as saying all three are girls. And so we know from part A the probability of that is one 8th. Now, the second case is one boy.