A generator driven by a wind turbine is required to deliver 12 MW of power at the generator terminal. The turbine is a two-blade propeller rotating about a horizontal axis, and the maximum permitted shear stress of the turbine shaft is 55x10^8 N/m^2. The rotor is designed to operate at a rotational speed of 70 revolutions per second. The stage efficiencies are Cp = 0.32, ngb = 90, and ng = 92. If the turbine delivers its rated power with an average wind speed of 20 m/s, calculate the corresponding diameter of the propeller and its TSR (Tip Speed Ratio) assuming a typical value for the overall efficiency. The air density may be assumed to have a value of 1.29 kg/m^3. (i) Calculate the torque on the turbine shaft, area, radius, and tip speed ratio.