The radial force on the particle is given by the Lorentz force. They don't give you the velocity so you have to solve for it in terms of the radius and get them to cancel.
The distance covered is simply the length of the entire trip, which is 12m + 16m, or 28m.
The displacement is the distance from the starting point to the ending point along with the direction of the net motion. The dog walks 12m east then 16m west, so its resultant displacement is 4m west.
The answer is reflection.
The drawing is simple but illustrates the concept beautifully.
The answer is true hope that helped!!