[填空题]
The nearest star to Earth is Proxima Centauri, 4:jf3ln/0hrndkq o;p5 .3 a*g 1d g;ok8f b4c:ehilight-years away.
(a) At what constant velocity must a spacecraft travel from Earth if it is to reach the star in 4.0 years, as measured by travelers on the spacecraft? c
(b) How long does the trip take according to Earth observers?$t_{Earth}$ = yr
