Relativity & Cosmology Problem No. 2

Problem No. 2 (Relativity and Cosmology) A star is ly from the Earth. At what speed must a spacecraft travel on its journey to the star such that the Earth-star distance measured in the frame of the spacecraft is ly? Reference PHYSICS for Scientists and Engineers with Modern Physics Raymond A. Serway John W. Jewett, Jr. Cengage 9th Edition (2014) Ch. No. 39 (Relativity) Exercise No. 39.5