A wind-turbine generator is designed to produce (3.5 x 10^6 kWhr) per year with an annual plant factor of 0.40. The design wind velocity is 45 km/hr. The conversion efficiency of wind is 0.5, and the mechanical (transmission) and generator efficiencies are 0.90 and 0.96 respectively. The ambient conditions are P = 100 kPa and T = 25 degrees Celsius Calculate the required rotor diameter and the power coefficient.