The two boxcars A and B have a weight of 21 000 lb and40 000 lb, respectively. They are freely coasting down the incline when the brakes are applied to all the wheels of car A. The coefficient of kinetic friction between the wheels of A and the tracks is μk = 0.6. The wheels of car B are free to roll. Neglect their mass in the calculation. Suggestion: Solve the problem by representing single resultant normal forces acting on Aand B, respectively. 

Determine the magnitude of the force in the coupling C between the two cars.

Express your answer to three significant figures and include the appropriate units.

T =

8.23 kip