5-32 A school currently pays $23,000 per year for the electricity it uses at a unit price of $0.11/kWh.The school management decides to install a wind turbine with a blade

diameter of 20 m and an aver-age overall efficiency of 30 percent in order to meet its entire electricity needs. What is the required average velocity of wind in this location? Take the density of air to be 1.2 kg/m' and assume the turbine operates at the required average speed 7500 h per year.