Astronomers on Earth, an Inertial Reference Frame, Observe Galaxies a and B

Multiple Choice

Astronomers on Earth, an inertial reference frame, observe galaxies A and B that are moving away from the Earth as shown. The speeds indicated are those measured by the astronomers on Earth. What is the speed of galaxy B as measured by an observer in galaxy A?

A) 0.22c
B) 0.60c
C) 0.71c
D) 0.95c
E) 1.42c