$15\mathrm{.}6\mathrm{.}44$

The volume $of$ a right circular cone with radius $r$ and height $hisV=r^2\frac{h}{3}.$

$a.$ Approximate the change $in$ the volume $of$ the cone when the radius changes from $r=6\mathrm{.}4tor=7\mathrm{.}1$ and the height changes from $h=4\mathrm{.}00toh=3\mathrm{.}94.$

$b.$ Approximate the change $in$ the volume $of$ the cone when the radius changes from $r=5\mathrm{.}16tor=5\mathrm{.}07$ and the height changes from $h=13\mathrm{.}0toh=12\mathrm{.}97.$

$a.$ The approximate change $in$ volume $isdV=$

$(Typean$ integer $or$ decimal rounded $to$ two decimal places $as$ needed.$)$