Water is draining out of a conical tank at a constant rate of 120 cubic inches per minute. How fast is the level of water in the tank decreasing when there are 7 inches of water in the tank?

a. The level of water in the tank is decreasing at a rate of 9.4 inches per min.

b. The level of water in the tank is decreasing at a rate of 3.1 inches per min.

c. The level of water in the tank is decreasing at a rate of 0.8 inches per min.

d. There is not enough information given.