Answer
$\mathop \smallint \limits_{}^{} \mathop \smallint \limits_S^{} f\left( {x,y,z} \right){\rm{d}}S = 50$
Work Step by Step
The surface integral of a function $f\left( {x,y,z} \right)$ is given by $\mathop \smallint \limits_{}^{} \mathop \smallint \limits_S^{} f\left( {x,y,z} \right){\rm{d}}S$.
Since $f\left( {x,y,z} \right) = 10$, so
$\mathop \smallint \limits_{}^{} \mathop \smallint \limits_S^{} f\left( {x,y,z} \right){\rm{d}}S = 10\mathop \smallint \limits_{}^{} \mathop \smallint \limits_S^{} {\rm{d}}S = 10 \times 5 = 50$