Evaluate the following by using cylindrical coordinates. ∫∫∫_b z dx dy dz, where b is the region within the cylinder x² + y² = 9 above the xy-plane and below the cone z = √(x² + y²)
a) ∫∫∫_b z r dr dθ dz
b) ∫∫∫_b z dz dr dθ
c) ∫∫∫_b z r dz dr dθ
d) ∫∫∫_b z dz dθ dr