So let's think about it. So our outer radius is going to be equal to what? Well, we can visualize it over here. This is our outer radius, which is also going to be equal to that right over there. So that's the distance between y equals 4 and the function that's defining our outside. The distance between y equals 4 and the function that is defining our outside. So this is essentially, this height right over here is going to be equal to 4 minus x squared minus 2x.