You may want to review (Pages 177 - 182).
For related problemsolving tips and strategies, you may want to view a Video Tutor Solution of Using work and energy to calculate speed.
Use the work-energy theorem to calculate the wagons final speed.
Use this acceleration in the kinematic relationship vx2 = v0x2 + 2ax (x - x0 ) to calculate the wagons final speed.
Calculate the acceleration produced by the force.