An 80 kg astronaut is stationary floating in free space. Another 80 kg astronaut is 100 m away, and moving at 2m/s away from the first astronaut. The first astronaut throws a hammer of mass 4kg at 10m/s to the second astronaut, which also causes the first astronaut to start moving backwards. When the second astronaut catches the hammer, how far apart are the two astronauts?

Can you please explain your answers.