So, let's do that sum. We're essentially just taking, we're just integrating both sides of this. And here, you might be able to do this in your head, or we could do the formal u substitution, just to make it clear what we're doing. If you said u is equal to w minus 300, then what is du? If you wanted the differential, so if you wanna take the derivative of u with respect to w, you would say du with respect to w is equal to what? It is equal to one. The derivative of this with respect to w is one.