A spaceship passes over an observation station on Earth. Just as the nose of the ship passes the station, a light in the nose of the ship flashes. As the tail o0f the ship passes the station, a light flashes in the ship's tail. According to an Earth observer, 50.0 ns elapses between the two events. In the astronaut's reference frame, the length of the ship is 12.0 m. 

(a) How fast is the ship traveling according to an Earth observer? 

(b) What is the elapsed time between light flashes in the astronaut's frame of reference?