1. Department of Quantitative Analysis, College of Business Administration, King Saud University, P. O. Box 71115, Riyadh 11587, Saudi Arabia
2. Department of Mathematics, Faculty of Science, Cairo University, Giza 12613, Egypt
3. Department of Mathematics, Faculty of Science, Galala University, Galala, Suez 43511, Egypt
4. Faculty of Engineering, Egyptian Russian University, Badr 11829, Egypt