So this is going to be 4 minus x. It's just going to be 4 minus x. So if we wanted to find the area of the face of one of these washers for a given x, it's going to be, and we can factor out this pi, it's going to be pi times the outer radius squared, which is all of this business squared. So it's going to be 4 minus x squared plus 2x squared. Minus pi times the inner radius, although we factored out the pi. So minus the inner radius squared. So minus 4 minus x squared.