Answer :

dwh2o13
For prisms:  V = Bh  where B is the area of the Base of the prism and h is the height of the prism.

B = 12(20) 
B = 240

Now let's substitute into:
V = Bh
4800 = 240h  divide both sides by 240
20 = h

So the height of the prism is 20 cm
The height is 20cm. Is it multiple choice?