Two fixed navigation beacons mark the approach lane to a star. the beacons are in line with the star and are 87 mm apart. a spaceship approaches the star with a relative velocity of 0.7 c and passes the beacons. as the ship passes the first beacon the ship emits a short radar pulse toward the second beacon, and the radar echo is received at the ship. the time interval between the emission of the radar pulse and the reception of the radar echo is closest to:
answer choices: 480 ms, 150 ms, 370 ms, and 340 ms