4. Two ships are moving toward each other with velocity of 0.7 c. At time zero in reference frame (reference frame of Earth), Ship 1 nearly collides with Earth and Ship 2 is at the distance of 105 km from Earth. (a)How long does it take according to the clock on Earth before the ships collide? What are the coordinates of each ship at the collision? (b)The clock in reference frame where Ship 1 is always at origin and at rest is set to zero when Ship 1 nearly collides with Earth. What will the clock in show when the two ships collide?