A four pole dc shunt generator with a wave wound armature having 390 conductors has to supply to a load of 500 lamps each of 100w at 250v.Allowing 10v for the voltage drop in the connecting leads between the generator and the load and drop of 2v. calculate the speed at which the generator should be driven. The flux per pole is 30m wb and the value of Ra=0.05 ohm and Rs= 65 ohm