And so what this basically means is this square here describes the event in which the first child is a boy, the second child is a boy, and the third child is also a boy. And because these events are basically independent of one another, we multiply their individual probability by the product rule to find the total probability of these independent events. So we have one half multiplied by one half multiplied by one half. And that gives us one eight. Now let's look at this block right here, this square. So this basically describes the probability.