1. Department of Mathematics, Faculty of Science, King Mongkut’s University of Technology, Thonburi (KMUTT) 1 , 126 Pracha Uthit Road, Bang Mod, Thrung Khru, Bangkok 10140, Thailand
2. School of Continuing Education, Bayero University 2 , Kano, Nigeria
3. Department of Mathematical and Statistics, University of Strathclyde 3 , Glasgow, United Kingdom
4. Department of Mathematical Sciences, Abubakar Tafawa Balewa University 4 , Bauchi, Nigeria