3 an observer in spaceship B obverses another spaceship A travelling with a velocity of 0.40 c relative to him. Both are moving in the +x-direction. the spaceship a fires a missile in the direction of its motion with a velocity of 0.70 c relative to A. if the distance of the spaceship A at the instant the missile is fired is 5c10^5 km, how much time it takes the missile to reach you (advise: attach S the spaceship B)