An object of known mass M with speed v0 travels toward a wall. The object collides with it and bounces away from the wall in the opposite direction in which the object was initially traveling. The wall exerts an average force F0 on the object during the collision. A student must use the equation Δp = FΔt to determine the change in momentum of the object from immediately before the collision to immediately after the collision. Which side of the equation could the student use to determine the change of the object's momentum?