Estimate $\int$ _R f(x, Y)dA Using the Table of Values Below, Where

Estimate $\int$ _R f(x, y)dA using the table of values below, where R is the rectangle 0 $\le$ x $\le$ 4, 0 $\le$ y $\le$ 6
$\begin{array}{c}y\\x\begin{array}{cccc}&0 & 3 & 6\\0 & 2 & 3 & 4 \\2 & 6 & 4 & 3 \\4 & 18 & 14 & 12\end{array}\end{array}$