A sled is being pulled on a frictionless icy surface, by a rope that is angled 45 degrees above the horizontal. The tension of the rope is 100 N. The sled is 50 kg. On top of the sled sits your pack of supplies, which has a mass of 20 kg. What is the coefficient of static friction that keeps your pack on the sled as it travels? Give your answer with three significant figures.