So I encourage you to pause this video and think through it and I'll give you a hint. What if we were to define the random variable m as equal to the height of a randomly selected man, height of random man. What if we defined the random variable w to be equal to the height of a random woman, woman, and we defined a third random variable in terms of these first two? So let me call this d for difference. And it is equal to the difference in height between a randomly selected man and a randomly selected woman. So d, the random variable d, is equal to the random variable m minus the random variable w. So the first two are clearly normally distributed. They tell us that right over here.