A tank is shaped like a circular cone with pointy end at the bottom. The tank is 28 ft deep and 14 ft across at the top, so the top of the tank is a circle with diameter = 14 ft. The tank is being filled with water at a rate of 15 $\text{ft}^3/\text{min}$. At what rate is the water inside the tank rising when the depth of the water is:

1. 1 foot? ft/min
2. 10 feet? ft/min
3. 27 feet? ft/min