First Author:   Meriem Sebai Faculty of Economic Sciences and Management of Tunis, Univerity of Tunis El-Manar, Tunisia meriemsebaii@gmail.com   Tunis, Tunisie       Second Author: Omar Talbi Faculty of Economic Sciences and Management of Tunis, Univerity of Tunis El-Manar, Tunisia omartalbi@live.fr   Tunis, 2092, Tunisie   52400172(Phone)