25. Draining a Tank It takes 12 hours to drain a storage tank by opening the valve at the bottom. The depth y of fluid in the tank t hours after the valve is opened is given by the formula 2 y = 6 1 m. 12 (a) Find the rate dy / dt ( m/h ) at which the water level is changing at time t. (b) When is the fluid level in the tank falling fastest? slowest? What are the values of dy / dt at these times? (c) Graph y and dy / dt together and discuss the behavior of y in relation to the signs and values of dy / dt