And so how do we do that? What's going to be equal to? Well, we could take the pi outside. It's going to be pi times the antiderivative of y, which is just y squared over 2, evaluated from 1 to 4, which is equal to pi times, well, you evaluate it at 4, you get 16 over 2. Let me just write it out like this. 4 squared over 2 minus 1 squared over 2, which is equal to pi times 16 over 2 is 8 minus 1 half. And so we could do this as 16 halves minus 1 half, which is equal to 15 halves.