An asteroid is moving along a straight line. a force acts along the displacement of the asteroid and slows it down. the asteroid has a mass of 4.3 × 104 kg, and the force causes its speed to change from 7600 to 5000 m/s. (a) what is the work done by the force? (b) if the asteroid slows down over a distance of 1.4 × 106 m determine the magnitude of the force.

i have part a, just need part b
a= -7.048e11 j