A 3-kg box is on a rough horizontal surface. An external force F is applied horizontally to the box. When force F equals 3.0 N, the box is in motion at constant velocity. The box slows down when force F is removed. The magnitude of the acceleration of the box when force F is removed is closest to:
0.1 m/s2
1 m/s2
0 m/s2
0.3 m/s2