1. Department of Mathematical Sciences, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa
2. Computational Science Program, College of Natural Science, Addis Ababa University, 1176 Addis Ababa, Ethiopia
3. Centre Universitaire d’Informatique (CUI), University of Geneva, Battelle Batiment A, Rte de Drize 7, 1227 Carouge, Switzerland