A wind turbine is rotating at 15 rpm

A wind turbine is rotating at 15 rpm under steady winds flowing through the turbine at a rate of 42,000 kg/s. The tip velocity of the turbine blade is measured to be 250 km/h. If 180 kW power is produced by the turbine, determine, (a) The average velocity of the air and, (b) The conversion efficiency of the turbine. Take the density of air to be 1.31 kg/m3.