And so this is the partial derivative with respect to m, that's that right over there, and we want to set this equal to 0. Now let's do the same thing with respect to b. This term, once again, is a constant from the perspective of b. There's no b here, there's no b over here, so the partial derivatives of either of these with respect to b is 0. Then over here, you have a negative 2n times the mean of y's as a coefficient on a b. So the partial derivative with respect to b is going to be minus 2n, or negative 2n times the mean of the y's. And then there's no b over here, and we do have a b over here, so it's plus 2mn times the mean of the x's.