A water trough is 2 ft deep and 10 ft long. It has a trapezoidal cross section with base lengths 2 and 5 feet.

- Find a relationship between the volume of water in the tank at any given time and the depth of the water at that time.

Where V= volume, L = length, D = depth of water

V = L [(b1 + b2)/2] D

V = 35D

- If water enters the trough at a rate of 10 ft^3/min, how fast is the water level rising (to the nearest 0.5 in./min) when the water is 1 ft deep.

V' = 35

Obviously, that doesn't work. Any advice?