Have you any idea of what this word is?
As for letter ש look at Rule 7.
And as regards נתארכה it is not difficult to realize that this is a PS-t type word.
Dictionaries have verb אָרַךְ, to be long, to last.
Oham has two patterns matching this word: PS-t1633 and PS-t1634. It is obvious that our word fits ptr PS-t1633.