Mathematics & Statistics Department, Faculty of Science, Taif University, Hawia(888)Taif, Saudi Arabia;
Department of Mathematics, Faculty of Science(Men), Al-Azhar University, Nasr City, Cairo, Egypt;
Department of Mathematics, Faculty of Science, Helwan University, Cairo, Egypt;
Basic Science Department, Faculty of Engineering, The British University in Egypt, Al-Shorouk City, Misr-Suez Desert Road, P.O.Box 43, Cairo 11837, Egypt;
