Find the area of the surface given by $f(x,y)=2x-2y-9$ over the region $R.$

$R$ : square with vertices $\{(0,0),(2,0),(2,3),(0,3)\}$

$2\sqrt[\phantom{2}]{9}$

$6\sqrt[\phantom{2}]{10}$

$6\sqrt[\phantom{2}]{9}$

$6\sqrt[\phantom{2}]{19}$