Someone in Earth's Rest Frame Says That a Spaceship's Trip $10.0 \mathrm { y }$

Multiple Choice

Someone in Earth's rest frame says that a spaceship's trip between two planets took $10.0 \mathrm { y }$ , while an astronaut on the space ship says that the trip took $5.78 \mathrm { y }$ . What is the speed of the spaceship, assuming the planets are at essentially at rest?

A) $0.816 \mathrm { c }$
B) $0.384 \mathrm { c }$
C) $0.735 \mathrm { c }$
D) $0.975 \mathrm { c }$