And then on the right-hand side, let's see, this cancels with that. We have xy plus 10y. And now let me take the derivative of both sides with respect to time. So the derivative of 20 times something with respect to time is going to be the derivative of 20 times something with respect to the something, which is just 20. That's the derivative of 20x with respect to x times dx, the derivative of x with respect to t, is equal to. Now, over here, we're going to have to break out a little bit of the product rule. So first, we want to figure out the derivative of x with respect to time.