1. Department of Mathematics, Yusuf Maitama Sule University Kano, Nigeria
2. Institute of Strategic Industrial Decision Modelling, School of Quantitative Sciences, Universiti Utara Malaysia, Sintok 06010, Malaysia
3. Faculty of Education and Arts, Sohar University, Sohar 311, Oman
4. Department of Mathematics, University of Botswana, Private Bag UB00704, Gaborone, Botswana
5. Department of Mathematics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok 16424, Indonesia