Mars has a mass of about 6.79 x 102³ kg, and its
moon Phobos has a mass of about 9.1 × 10¹5 kg. If
the magnitude of the gravitational force between
the two bodies is 4.98 x 10¹5 N, how far apart are
Mars and Phobos? The value of the universal
gravitational constant is
6.673 x 10-¹¹ N. m²/kg².
Answer in units of m.