The state of Iowa is among the top three states in U.S. in wind power generation. In 2016, over 20 billion kWh of electrical energy in Iowa was generated by wind power. Assuming that wind speed at the altitude of wind turbine is in average of 6 m/s, the efficiency of converting wind energy to the electricity is 80 %, and all wind turbines work constantly throughout the year. We can further assume that the air in Iowa has an average temperature of 11 °C and the air pressure of 97.5 kPa at the height of wind turbine, and the turbine has a 12-m diameter flow section. Complete the following calculations:

(a) Estimate the wind energy for unit mass of wind flow (J/kg) operating on a turbine.

(b) Estimate the mass flow of the turbine.

(c) () Estimate the wind power per turbine.

(d) Estimate how many wind turbines we have in the state of Iowa?