(9)Tlie drag of an airfoil at zero angle of attack is liinction of density, viscosity, velocity, and a length parameter. A 1/10 scale model of an airfoii was tested in a wind Uuinel ai a Reynolds ntimber of 5.5x 106, based on chord length. Test conditions in the wind lunnel air stream were 15°C and 10 atm absolute pressure. The prototype aiifoil has a chord length of 2 m, and is to be flown in air at standard conditions. Determine the speed at wliich the wind tunnel model was tested, and the corresponding prototype speed. (20 分)