Answer
$\approx 64.0$
Work Step by Step
Approximate the double integral with a Riemann sum; to use a nine term sum for this square area $R$, the $x$ and $y$ variables should have three terms.
$\int\int f(x,y)dA\approx \Sigma _{i=1}^{3}\Sigma _{j=1}^{3}f(x_{i}y_{j}) \triangle A$
Here, $\triangle A =1 \times 1$
$=f(1,1)+f(1,2)+f(1,3)+f(2,1)+f(2,2)+f(2,3)+f(3,1)+f(3,2)+f(3,3)$
$\approx 2.5+4.5+8.0+5.0+7.0+10.0+6.5+8.5+12.0$
$\approx 64.0$
