Well, what's the outside radius? The radius that goes to the outside of the washer. Well, that's f of x. So it's gonna be f of x is the radius, and we're just going to square that. So that would give us, this expression right over here would give us the area of the entire face if it wasn't a washer, if it was a coin. But now we have to subtract out the inside. So what's the area of the inside?