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. So this is equal to 15 halves times pi. Or another way of thinking of it is 7 and 1 half times pi. But this is a little bit clearer.