Given an inverted cone whose height is tall, has an opening radius of , and full of water at the beginning. The water drains at a rate of . The water level is continuously dropping as the result. At what rate is the water level falling when the water is halfway down the cone?
and radius 
(at the top). If water is poured into the cup at a rate of 
, how fast is the water level rising when the water is 
deep?
. The base radius of the tank is 
and the height of the tank is 
. At what rate is the depth of the water in the tank changing when the radius of the top of the water is 
?