The power available from a wind turbine is calculated by the following equation: upper p equals one half upper a rho nu cubed where pequalspower [watts], aequalssweep area (circular) of the blades [square meters], rhoequalsair density [kilograms per cubic meter], and nuequalsvelocity [meters per second]. the world's largest sweep area wind turbine generator in spain has a blade diameter of 420 feet [ft]. the specific gravity of air is 0.00123. assuming a velocity of 30 miles per hour [mi/h] and the power produced is 5 megawatts [mw], determine the efficiency of this turbine.