Affiliation: | 1. Institute for Groundwater Studies, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein 9300, South Africa;2. Department of Mathematical Sciences, Federal University of Technology, Akure, PMB 704, Ondo State, Nigeria;3. Achieversklub School of Cryptocurrency and Entrepreneurship, 1 Sturdee Avenue, Rosebank 2196, South Africa;4. Department of Mathematics and Applied Mathematics, University of Pretoria, Pretoria 002, South Africa |