So this is going to be, we're taking the partial derivative with respect to m, so it's going to be 2 times, so it's going to be plus 2 times, 2 times n times the mean of the x squared times m, right? The derivative of m squared is 2m, and then you just have this coefficient there as well. Now this term, you also have an m over there, so let's see. 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.