These two questions are giving me some trouble. I can see that z = r^2, by using polar coordinates but after that i don't know what to do.

First Question

1.) Find the volume lying between the paraboloids:

z = x^2 + y^2 and 3z = 4-x^2-y^2

Second Question

2.) Find the volume lying inside both the sphere x^2 + y^2 + z^2 = 2a^2

and the cylinder x^2 + y^2 = a^2

Any help would be much appreciated, thanks guys/girls