Solve the Problem $z = \sqrt { 36 - x ^ { 2 } - y ^ { 2 } }$

Multiple Choice

Solve the problem.
-Find the center of mass of the hemisphere of constant density bounded $z = \sqrt { 36 - x ^ { 2 } - y ^ { 2 } }$ and the $x y - p l a n e$ .

A) $\bar { x } = 0 , \bar { y } = 0 , \bar { z } = \frac { 9 } { 4 }$
B) $\bar { x } = 0 , \bar { y } = 0 , \bar { z } = 4$
C) $\bar { x } = 0 , \bar { y } = 0 , \bar { z } = \frac { 3 } { 2 }$
D) $\bar { x } = 0 , \bar { y } = 0 , \bar { z } = 2$