Dresden, Germany Has a Population of 700,000 and a Population $2200 \mathrm {~km} ^ { - 2 }$

Dresden, Germany has a population of 700,000 and a population density of $2200 \mathrm {~km} ^ { - 2 }$ in the urban area. Assume that the electrical needs of Dresden are an average of $1.0 \mathrm {~kW} _ { \mathrm { e } }$ per capita and these are satisfied by a wind farm consisting of $100 \mathrm {~m}$ diameter three-rotor wind turbines operating at optimal efficiency and with optimal spacing. If the wind velocity is constant at $7 \mathrm {~m} / \mathrm { s }$ , what is the area of the wind farm relative to the area of the urban area it serves?