As Measured in Earth's Rest Frame, a Spaceship Traveling at 0.9640c

Multiple Choice

As measured in Earth's rest frame, a spaceship traveling at 0.9640c takes $10.5 \mathrm { y }$ to travel between two planets that are not moving relative to each other. How long does the trip take as measured by someone on the spaceship?

A) 2.79 y
B) 6.83 y
C) 39.5 y
D) 28.8 y