Related Rate question regarding application of the deriviative..

I have tried this problem, but it's not working out.

Sand poured on the ground at a rate of 3 meters cubed per minute forms a conical pile whose height is 1/3 the diameter of the base. How fast is the altitude increasing when the radius of the base is 2 m.

First I replace r in the conical V=1/3 PIE r^2h

I take h = 1/3 d

h=1/3(2r)

So I get r = 3h/2

So then I put it in V=1/3 PIE (3h/2)^2h

When I do the derivative I get

dV/dt=3PIEh^2 dh/dt

I plug in the numbers

3=3PIE(2)^2 dh/dt

and get .0795 m/min

But the answer is .239m/min

What am I doing wrong in this problem, if someone can help thanks.

Joanne