A wind turbine with a 90m-diameter rotor is rotating at 30 rpm under steady winds at an average velocity of 25 km/h. Assuming the turbine has an efficiency of 32%, determine a) the power produced, kW; b) the tip velocity of the blade, in km/h; c) the revenue generated by the wind turbine per year if the electric power produced is sold at $0.05/kWh. Take the density of air to be 1.20 kg/m3. 2. Helium is to be compressed from 120 kPa and 310 K to 700 kPa and 430 K. A heat loss of 20 kJ/kg occurs during the process. Neglecting kinetic energy changes, determine the power input required for a mass flow rate of 90 kg/min.