1. School of Mathematics, Statistics and
Computer Science, University of Kwazulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa e-mail:
2. Department of Applied Mathematics, Indian School of Mines, Dhanbad 86004, India e-mail:
3. Institute for Advance Researchin Mathematical Modelling and Computations, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535, South Africa e-mail:
4. School of Petroleum Technology, Pandit Deendayal Petroleum University, Gandhinagar 382007, India e-mail: