School of Science, Engineering and Technology, Department of Mathematics and Statistics, Mulungushi University, Kabwe, Zambia
Department of Mathematics, University of Botswana, Gaborone, Botswana
Copyright © 2018 George M. Mukupa, Elias R. Offen et al. This is
an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.