the speed 40km/h

The aerodynamic drag of a new sports car is to be predicted at a speed of 40km/h at an air temperature of 25C. A one-third scale model of the car was built to test in a wind tunnel. The temperature of the wind tunnel air is also 25C. The drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground (from the car's frame of reference). Determine how fast the engineers should run the wind tunnel to achieve similarity between the model and the prototype