Turbines are to be installed where the net head is 400 ft and the flow rate is 250,000 gal/min. Discuss the type, number, and size of turbine which might be selected if the generator selected is (a) 48-pole, 60-cycle (n =150 rpm); or (b) 8-pole (n = 900 rpm). Why are at least two turbines desirable from a planning point of view?