A spaceship with proper length 1000m moves away from a space station in the +x

direction at a speed 0.6c relative to an observer on the station. An astronaut stands at

the rear of the spaceship and fires a dart towards the front of the spaceship at a speed

of 0.8c relative to the spaceship. How long does it take the dart to reach the front of the

spaceship:

a) as measured in the frame of the spaceship?

b) as measured in the frame of the space station?

c) as measured in the frame of the dart?

Please describe the procedure in details !!