Default unroot att one x and flash stock rom (s-off)

Hi everyone,

I have an old at&t htc one x I want to sell, and it is currently rooted

evita pvt ship s-off rl
hboot - 2.18.0000

I looked at the HTC's webpage, and found this

On the bottom of the page, there is a download link for RUU (5.18.502.1.exe). Is that the file I should use?

if that is not the right RUU file, can someone link me to the correct file? Thank you so much!