The affix ac comes after the word nāsikā final in a bahuvrīhi samāsa when an upasarga (Preposition) precedes it and nas is substituted for nāsikā,
This rule applies where the word is not a sanjna, as it was in the last. Thus उन्नता नासिकास्य = उन्नसः, प्रणसः ॥ The न is changed into ण by 8.4.28.
Vart:- The ग्र substituted for नासिका when वि precedes it. As, विगतानासिकाऽस्य = विग्रः, so also विख्यः in the same sense.,