Find the Mass of the Surface S Having the Given $x + y + 3 z = 3$

Find the mass of the surface S having the given mass density. S is part of the plane $x + y + 3 z = 3$ in the first octant; the density at a point P on S is equal to the square of the distance between P and the xy-plane.

A) $\sqrt { 11 }$
B) $\frac { \sqrt { 11 } } { 4 }$
C) 49
D) 20