Use triple integral to find volume

Hi guys

please I realy need your help with 3 problems

1- Use triple integral to find the volume of the solid in the first octant bounded by the coordinate planes, the plan y=1, and the parabolic cylinder z= 9-x^2.

2-Find the volume of the region bounded above by the paraboloid z=9-x^2-y^2, below by the xy-plane, and that lies outside the cylinder x^2+y^2=1.

3- (a) find the center of mass of a solid of constant density bounded below by the paraboloid z=x^2+y^2 and above by plane z=4.

(b) Find the plane z=c that divides the above solid into two part of equal volume. (This plane dose not pass through the center of mass).

Please friends help me as best as you can.