31. a spaceship approaches a planet with a speed 0.6c. at some point it fires a projectile with a speed 0.4c towards the planet. the speed of the projectile, as

31. A spaceship approaches a planet with a speed 0.6c. At some point it fires a projectile with a speed 0.4c towards the planet. The speed of the projectile, as seen by an observer on the planet would be approximately (a) 0.76c (b) 0.80c (c) 0.99c (d) 0.40c