Evaluate the Surface Integral of G Over the Surface S $x + y + z = 1$

Multiple Choice

Evaluate the surface integral of G over the surface S.
-S is the plane $x + y + z = 1$ above the rectangle $0 \leq x \leq 3$ and $0 \leq y \leq 5 ; G ( x , y , z ) = 6 z$

A) 360
B) $180 \sqrt { 3 }$
C) $- 270 \sqrt { 3 }$
D) $- 180$