decrease yeah free 100 percent
8 wave units I guess I tried it should be the answer though
By Newton's second law, we have

So, in order to give a 0.15kg body an acceleration of 40m/s^2, you need a force of

A.Positive as work=force×distance (assuming that distance is always a constant) the work will always be positive as the force is always positive(this is because force=mass×acceleration where the acceleration is always positive unless the mass is being slowed down)