Use a Riemann sum to estimate the volume of the solid that lies below the surface $z = xy$ and above the region $R = \lbrace (x,y): 0 \le x \le 3, 0 \le y \le 6\rbrace$. Create the Riemann sum by subdividing $[0,3]$ into $m = 3$ intervals, and $[0,6]$ into $n=2$ intervals, and take the sample point to be the upper right corner of each rectangle.

Volume: