Water is leaking out of a tank. The amount of water in the tank t minutes after it springs a leak is given by W(t) gallons. (a) Explain what dW dt means in practical terms. dW dt tells us the amount of water drained from the tank in a minute's time. dW dt tells us the amount of water left in the tank after a minute's time. dW dt tells us the change in the amount of water in the tank we expect in a minute's time. (b) As water leaks out of the tank, is dW dt positive or negative