A truck is designed to measure concrete roughness. During a typical test the driver will bring the vehicle to a constant test velocity, v, and then suddenly lock the brakes bringing the vehicle to a complete stop. Knowing the total stopping distance, d, an evaluation of the pavement roughness can be made. During a test on I-25, the vehicle had a total mass of 20 Mg, initial velocity of 30 m/s, and stopping distance of 110m. Estimate the effective coefficient of friction between this runway and the trucks tires.