A water tank has the shape obtained by revolving the parabola x^2=by around the y-axis. The water depth is 4ft at noon when a circular plug at the bottom of the tank is removed. At 1pm the depth of the water is 1ft. a)find the depth y(t) of water remaining after t hours b)when will the tank be empty? c)if the initial radius of the top surface of teh water is 2ft, what is the radius of the circuluar hole in the bottom by using dV/dt=-a(2y)^(1/2) where a is the area of the bottom of the hole of the tank, I solved parts a and b. I found a) y=(8-7t)^(2/3) and b) 1.143 hrs. I am having trouble with part c. Can you help? Thanks.