And then, of course, my base of my whole thing. So this whole region right over here of my piece of cardboard would be the floor of this box that I'm constructing. And what I want to do is I want to maximize the volume of this box. I want to maximize how much it can hold. And I want to maximize it by picking my x appropriately. So let's think about what the volume of this box is as a function of x. In order to do that, we have to figure out all the dimensions of this box as a function of x.