The rate at which water leaks from a tank, in gallons per hour, is modeled by R, a differentiable function of the number of hours after the leak is discovered. Which of the following is the best interpretation of R'(3) ? (A) The amount of water, in gallons, that has leaked out of the tank during the first three hours after the leak is discovered B) The amount of change, in gallons per hour, in the rate at which water is leaking during the three hours after the leak is discovered C) The rate at which water leaks from the tank, in gallons per hour, three hours after the leak is discovered D) The rate of change of the rate at which water leaks from the tank, in gallons per hour per hour, three hours after the leak is discovered