Salt is being poured onto a conical pile with a constant radius of 20 meters. The twice-differentiable function $V(t)$ gives the volume of the pile in $\text{m}^3$ with $t$ measured in seconds. The table gives selected values of $V^{\prime}(t)$ at various times during the interval $0 \leq t \leq 15$. The formula for the volume of a cone is $V=\frac{1}{3} \pi r^2 h$. At time $t=5$ seconds, the height of the pile is 12 m. At what rate is the height of the pile changing when $h=12$ m?

$t$ (sec)	0	5	10	15
$V^{\prime}(t)\left(\text{m}^3 / \text{sec} \right)$	4	6	7	8