I have a group of problems that deals with the equations: f(x,y)= x^2+y^2 g(x,y)=20-(x-4)^2-(y+2)^2. I know that the surfaces z=f(x,y) and z=g(x,y) intersect in a closed curve, C, and the projection of C onto the xy-plane is a circle. However, I am having trouble finding its xy-equation, center, and radius. Additionally and more importantly, I am in the dark on setting up the double or triple integral for the volume of the region bounded by z=f(x,y) and z=g(x,y). Can anyone please help.