Problem $11.$ Let $f(x,y)=16xy-9x^2$ and $D=\{(x,y)$:$2x3,-1y1\}.$

$(a)$ Compute the volume under $f$ over the region $Dby$ integrating with respect $tox$ first:

${}_{D}f(x,y)dA={\displaystyle \underset{y=-1}{\overset{1}{}}}{\displaystyle \underset{x=2}{\overset{3}{}}}(16xy-9x^2)dxdy$

$(b)$ Compute the volume under $f$ over the region $Dby$ integrating with respect $toy$ first:

${}_{D}f(x,y)dA={\displaystyle \underset{x=2}{\overset{3}{}}}{\displaystyle \underset{y=-1}{\overset{1}{}}}(16xy-9x^2)dydx$

Which order $of$ integration was easier?