I have a couple of double integrals that I am having troubles with. I think for both of them it would be a good idea to use polar coordinates, but I am still having trouble setting them up/solving them.

a) Double Integral (x dA), over D, where D is the region in the first quadrant that lies between the circles (x^2) + (y^2) = 4 and (x^2) + (y^2) = 2x.

b) Find the volume of the given solid: inside the sphere (x^2) + (y^2) + (z^2) = 16 and outside the cylinder (x^2) + (y^2) = 4.

Thanks for any help.