I need to set this up as a double integral.

So the region of integration on the xy-plane should be or,

If I take the region in the first quadrant, I end up writing

The answer I have in the book gives the constant as 8, instead of 4. I'm not understanding why this is. I'm integrating over 1/4 of the region defined by , so I'm just multiplying it by 4 to account for the rest of the region....