Well, I would add these two means. It would be three plus four, it would be equal to seven. So in this particular case, it is equal to three plus four, which is equal to seven. And similarly, if I were to ask you the difference, if I were to say, well what's the, how many more cats in a given day would I expect to see than dogs, so the expected value of Y minus X? What would that be? Well, intuitively, you might say, well, hey, if we can add random, if the expected value of the sum is the sum of the expected values, then the expected value or the mean of the difference will be the differences of the means, and that is absolutely true. So this is the same thing as the mean of Y minus X, which is equal to the mean of Y, is going to be equal to the mean of Y minus the mean of X minus the mean of X, and in this particular case, it would be equal to four minus three, minus three is equal to one.