blade speed ratio

If $$\,\,{V_N}\,\,$$ and $$\alpha $$ are the nozzle exit velocity and nozzle angle in an impulse turbine, the optimum blade velocity is given by

For a single stage impulse turbine with rotor diameter of $$2$$ $$m$$ and a speed of $$3000$$ $$rpm$$ when the nozzle angle is $${20^0},$$ the optimum velocity of steam in $$m/s$$