An inverted conical water tank with a height of $6$ meters and a radius of $3$ meters is drained through a hole in the vertex at a rate of $9$ meters cubed per second. What is the rate of change of the water depth when the water depth is $3$ meters?
Remember: The volume of a cone is $\frac{1}{3}\pi r^2 h$.

$\left.\frac{dh}{dt}\right|_{h=3} =$
You can enter in $\pi$ as "pi".

(you will lose 25% of your points if you do)