And this gives us by the product rule. So this multiplied by this a value of one fourth. So essentially we take one half multiplied by one half because the probability of getting a girl the first time around is one half and the probability of getting a girl the second time around is also one half. And so we get a value of 00:25 or one four or equivalent to 25%, whichever way you want to actually look at it. Okay, so now that we have the product rule, let's actually move on to the sum rule. So let's take a look at what the sum rule tells us.