A simple impulse turbine expands steam frictionlessly from 12 bar, 250 0C with an enthalpy of 2935 k J/kg to n enthalpy of 2584 k J/kg at 0.1 bar. Assuming that the nozzle makes an angle of 20 0 with the blade motion, and that he blades are symmetrical, find the blade velocity that produces maximum efficiency for a turbine speed of 3600 rev/min. Assume that the steam enters the nozzle with negligible velocity.