Question

1) An astronomer observes an AGN with a radio jet. Over a period of 3.9 years, the astronomer observes a mass of luminous material in the jet travel 7.7 light-years across the sky. What is the apparent transverse velocity of the material in terms of a multiple of the speed of light c?

For this question I originally used the the Lorentz transformation for Time, but I realized this probably is incorrect because light years and years won't cancel out.

Answer 1