Çözüldü Special Relativity Theory

A slightly harder test adaptation of a solved problem in a book:

If the pilot of a spaceship shooting past the earth parallel to the earth's surface in the velocity magnitude which is half of the light speed at an altitude of √3 kilometers from the surface holds a 50 cm long ruler perpendicular to the direction of ship's motion, what would the length of this ruler be measured on a device used by an observer on earth?
A) 25·√3 cm
B) 25 / √3 cm
C) 50·√3 m
D) 5 / √3 m
E) 0.5 m


https://i72.servimg.com/u/f72/19/97/10/39/relati10.png
https://ia802804.us.archive.org/21/...InPhysics/3000 solved problems in physics.pdf
[Page 694 (720 in the pdf file), Problem 37.21]