An observer on Earth observes Planet X to be 16 light-years away and stationary. An observer in a spaceship passing Earth on its way to Planet X observes Planet X to be 9.6 light-years away. According to the observer in the spaceship, it takes years between Earth passing by and Planet X passing by. a) 10 years.
b) 12 years.
c) 14 years.
d) 16 years.
e) 18 years.