An astronaut is in a spaceship traveling at constant velocity toward the star Rigel and is far away from any other objects (planets and stars, etc.). There is racquet ball moving at 0.5 m/s on the spaceship. An astronaut blows air on the racquet ball, producing a small force of 0.08 N in the direction opposite the ball's velocity. The ball slows to a stop in 4 s.
What is the mass of the racquet ball?