Use Spherical Coordinates to Find the Z Coordinate of the Center

Multiple Choice

Use spherical coordinates to find the z coordinate of the center of mass of the solid lying between two concentric hemispheres of radii 6 and 7, and having uniform density k.

A) $\bar { z } = \frac { 36,124 } { 15 } k \pi$
B) $\bar { z } = \frac { 36,124 } { 15 } k$
C) $\bar { z } = \frac { \pi k } { 36,124 }$
D) $\bar { z } = \frac { 3,315 } { 1,019 } k$
E) $\bar { z } = \frac { 15 } { 36,124 } k \pi$