So now that we know what the product and the sum rule is, let's take a look at the following example that applies those two rules. Let's begin by stating the problem. So if a couple decides to have three children total, what is the probability that A all three are girls, b all three children are boys? C the first one is a boy, the second child is a girl girl, and the third one is a boy? D two of them are boys and one of them is a girl, and E they produce, at most, two boys. So let's begin by creating the Punnett square.