Where does the accent mark ( ' ) or breve ( u ) go in the sentence below? in quiet she reposes;

The breve mark is used to indicate short vowels, vowels which are not emphasized in a sentence. So, in this case it could be placed above the following syllables: in, -et, re- and -ses.

The accent mark is used to indicate the vowel where the emphasis is placed. So, in this case it could be placed above the following syllables: qui-, she, and -po-.