Affiliation: | 1. School for Computer, Statistical and Mathematical Sciences, North-West University, South Africa;2. School of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, PO WITS 2050, South Africa1;3. Department of Finance and Investment Management, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa2;4. Dipartimento di Matematica e Informatica, University of Palermo, Via Archirafi 34, 90123 Palermo, Italy |