Values of \(f(x, y)\) are given in the table below. Let \(R\) be the rectangle \(1
\leq x \leq 1.6,2 \leq y \leq 3.2\). Find a Riemann sum which is a reasonable
estimate for \(\int_{R} f(x, y) d a\) with \(\Delta x=0.2\) and \(\Delta y=0.4 .\)
Note that the values given in the table correspond to midpoints.
$$
\begin{array}{|c||c|c|c|}
\hline y \backslash x & 1.1 & 1.3 & 1.5 \\
\hline \hline 2.2 & 4 & 2 & -1 \\
\hline 2.6 & 5 & 2 & 0 \\
\hline 3.0 & 9 & -5 & 0 \\
\hline
\end{array}
$$
\(\int_{R} f(x, y) d a \approx\) _______________________.