1. Department of Mathematics, University of Calabar, Calabar, Nigeria
2. Department of Mathematics, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
3. Department of Basic Engineering, Faculty of Engineering, Menoufia University, Shibin el Kom 32511, Egypt
4. School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban, South Africa