Question regarding Geometry - Volumes

[thegmatexperience]

Good morning,

I have a problem with understanding the following problem and its solution:

"A closed cylindrical tank contains 36Ï€ cubic feet of water and is filled to half its capacity. When the tank is placed upright on its circular base on level ground, the heigth of the water in the tank is 2 feet. When the tank is placed on its side on level ground, what is the height, in feet, of the surface of the water above the ground?"

A) 2
B) 3
C) 4
D) 6
E) 9

This is how I would do it:
Now we remember the formular for the volume of a cylinder. It is r^2*Ï€*height.
The volume of the water in the tank is 36Ï€. So the volume of the entire tank is 72Ï€. Because we need to know what the radius of the cylinder is, we plug in all we know and solve the equation for r.

If I made an mistake it is obviously located at my calculation of the volume. OG's solution is 3.

Can somebody help me with this please?

[Anurag@Gurome]

A closed cylindrical tank contains 36Ï€ cubic feet of water and is filled to half its capacity. When the tank is placed upright on its circular base on level ground, the height of the water in the tank is 2 feet. When the tank is placed on its side on level ground, what is the height, in feet, of the surface of the water above the ground?

It should be 4 feet.

Radius of the base = √[(Volume of water)/(π*(Height of water))] = √[36π/(4π)] = √9 = 3

[thegmatexperience]

Thanks, yes it should be. Obviously a mistake in the OG.