And you can see, these are just going to be numbers here. So our change in u, this would cancel with that, and you'd be left with change in y over change in x, which is exactly what we had here. So nothing earth-shattering just yet. But what's this going to be equal to? What's this going to be equal to? Well, the limit of the product is the same thing as the product of the limits. So this is going to be the same thing as the limit as delta x approaches zero of, and I'll color-code it, of this stuff, of delta y over delta u times, maybe I'll put parentheses around it, times, times the limit, the limit as delta x approaches zero, delta x approaches zero of this business.