In the first place, I would like to express my earnest thanks to my advisor, Dr. Dribissa Dufera ,rnfor his unreserved professional and technical assistance in framing, actualizing and culminatingrnthe study.rnNext, I strongly expound my deep appreciation to my true friend Dilnesaw Asrat for hisrnunforgettable and worthy support and encouragement during the past two years.rnThen, I would like to pass my words of thanks to my whole family, owing in fact the highestrncredits to my younger sister Yitayish Wasyhun and my cuisine Selamawit Hailu.rnLastly, I express my deep appreciation to the CERTWID and its beloved staff members forrnproviding me fund for conducting the study.