A 50% efficient hydroelectric plant generates electricity from water falling a height of 110 m and at a rate of R kg/s. If the maximum possible power output of the plant is 27.0 MW, what is R? A) 510 103 kg/s B) 5.1 103 kg/s C) 100 103 kg/s D) 50 103 kg/s E) 55 103 kg/s