1. Department of Mathematics and Statistics, Imam Mohammad Ibn Saud Islamic University College of Science , 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 Mathematics, College of Science, King Saud University , P.O. Box 1142 , Riyadh 11989 , Saudi Arabia