Deimos, a satellite of Mars, has an average radius of 6.3×10³ m. If the gravitational force between Deimos and a 3.0 kg rock at its surface is 2.5×10⁻² N, what is the mass of Deimos?
A. 5.0×10²⁰ kg
B. 7.5×10¹⁹ kg
C. 1.0×10²¹ kg
D. 3.0×10²² kg