If $\rho ( x , y , z ) = z$

Multiple Choice

If $\rho ( x , y , z ) = z$ is the mass density of the solid in the first octant inside $x ^ { 2 } + y ^ { 2 } = 4 x$ and under $x ^ { 2 } + y ^ { 2 } + z ^ { 2 } = 16$ then its total mass is

A) $11 \pi$
B) $10 \pi$
C) $9 \pi$
D) $\frac { \pi } { 2 }$
E) $\frac { 4 \pi } { 5 }$