Answer:

Step-by-step explanation:
For sound waves we have v=d/t where v is the speed of sound and d the distance between the astronauts, while for electromagnetic waves we have c=D/t where c is the speed of light and D the distance between the spaceship and Earth. We have written both times as the same because is what is imposed by the problem, so we have t=d/v=D/c, which means:

And for our values:
