Everything else is just kind of a coefficient on this m, so the derivative with respect to m is 2bn times the mean of the x's. If I took the derivative of 3m, the derivative is just 3, it's just the coefficient on it. And then finally, this is a constant with respect to m, so we don't see it. 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.