A 4 kg box is at rest on a table. The static friction coefficient u, between the box and table is 0.30, and the kinetic friction coefficient Hi is 0.10. Then, a 10 N horizontal force is applied to the box.

Under the action of a constant force an object accelerates at 7.8 m/s2. what will the acceleration be if (a) the force is halved? (b) the object's mass is halved? (c) the force and the object's mass are both halved? (d) the force is halved and the object's mass is doubled?