Evaluate ∬R(x+y)dA\iint_R (x + y) dA∬R(x+y)dA over the region RRR bounded by x=0,y=0,x+y=1x=0, y=0, x+y=1x=0,y=0,x+y=1.
16\frac{1}{6}61
13\frac{1}{3}31
12\frac{1}{2}21
111