1. Department of Mathematics and Statistics, College of Science, Imam Mohammad Ibn Saud Islamic University, P.O. Box 90950, 11623, Riyadh, Saudi Arabia
2. Institute for Groundwater Studies, Faculty of Natural and Agricultural Science, University of the Free State, 9300 Bloemfontein, South Africa
3. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan
4. Department of Mathematics, College of Science, King Saud University, P.O. Box 1142, Riyadh 11989, Saudi Arabia