A 40-Mg boxcar A is moving in a railroad switchyard with a velocity of 9 km/h toward cars B and C, which are both at rest with their brakes off at a short distance from each other. Car B is a 25-Mg flatcar supporting a 30-Mg container, and car C is a 35-Mg boxcar. As the cars hit each other they get automatically and tightly coupled. Determine the velocity of car A immediately after each of the two couplings, assuming that the container

(a) Does not slide on the flatcar,

(b) Slides after the first coupling but hits a stop before the second coupling occurs,

(c) Slides and hits the stop only after the second coupling has occurred.

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9 kmh