Two Astronauts, of Masses 60 Kg and 80

Multiple Choice

Two astronauts, of masses 60 kg and 80 kg, are initially right next to each other and at rest in outer space. They suddenly push each other apart. How far has the heavier astronaut moved when the lighter astronaut has moved 12 m?

A) 7.0 m
B) 16 m
C) 21 m
D) 9.0 m
E) 12 m