13. A “race rocket” completes one straight leg of a lap in an

“outer space” race at a constant speed of 0.9c. The race organizers have carefully laid out this leg to be exactly 0.100 light-years long. Which observer(s) (if any)

measure the leg’s proper length:

(a) the organizers,

(b) the driver of the rocket,

(c) both the organizers and the driver, or

(d) neither?