Two horizontal forces F1 and F2, are acting on a box, but only F1 is shown in the drawing. F2 can point either to the right or to the left. The box moves only along the x-axis. There is no friction between the box and the surface. Suppose that F1 = +7.7 N and the mass of the box is 4.2 kg. Find the magnitude and the direction of F2 when the acceleration of the box is +4.5 m/s^2, -4.5m/s^2, and 0 m/s^2.