A planet outside our solar system has 18 times the mass and 3 times the radius of the Earth. What will be the magnitude of the gravitational acceleration on the surface of this planet? O 12.5 m/s2 20 m/s2 O 15 m/s2 12 m/s2 O 8 m/s2 O 7.5 m/s2 6 m/52