The distance between magnetic field lines indicates a. whether the magnet will attract or repel another magnet b. the strength of the magnetic field c. the direction of the magnetic field

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?