A trailer truck is travelling on the interstate with a speed of 72 km/hr. The trailer has a 1- ton cab and a 5-ton trailer. The braking system for the front and middle wheels prevent the wheels from sliding, while the braking in the rear wheels is not functioning. Knowing that the coefficient of static friction is 0.5, determine (a) the shortest time for the truck to come to a stop, (b) the horizontal force in the coupling during that time. Assume that the trailer weight is uniformly distributed and that it is partially supported by the cab