So minus 4 minus x squared. So this will give us the surface, the surface there, or the area of the surface or the face of one of these washers. If we want the volume of one of those washers, we then just have to multiply times the depth dx. We just multiply times the depth dx. And then if we want to actually find the volume of this entire figure, then we just have to sum up all of these washers for each of our x's. So let's do that. So we're going to sum up the washers for each of our x's and take the limit as they approach 0.