An Object Is Released from Rest When It Is a Height

An object is released from rest when it is a height h above the surface of a planet of mass M and radius R. What is the speed of the object just before striking the surface of the planet? Neglect any air resistance. Let h = 4.0 × 106 m, R = 5.0 × 106 m, and M = 4.0 × 1024 kg.

A) 7.8 km/s
B) 3.5 km/s
C) 5.4 km/s
D) 6.9 km/s
E) 4.8 km/s