11.9. Conical water reservoir. Water is flowing into a conical reservoir at a rate of 4 m' / min. The reservoir is 3 m in radius and 12 m deep. (a) How fast is the radius of the water surface increasing when the depth of the water is 8 m? (b) In (a), how fast is the surface rising? 11.10. Sliding ladder. A ladder 10 meters long leans against a vertical wall