A space probe of mass \(m\) is launched from the surface of a planet of mass \(M\) and radius \(R\). The graph below shows the magnitude of the gravitational force \(F_g\) exerted by the planet on the probe as a function of the distance \(r\) from the planet's center. When the probe is at a distance \(r = R\), the gravitational force has a magnitude of \(F_0\). Which of the following correctly describes the magnitude of the gravitational force when the probe reaches a distance \(r = 2R\)?