1. School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban, South Africa
2. Department of Mathematics, University of Calabar, Calabar, Nigeria
3. Department of Mathematics, University of Eswatini, Private Bag 4, Kwaluseni, Eswatini
4. Department of Mathematics and Applied Mathematics, Sefako Makgatho Health Sciences University, Medunsa 0204, Pretoria, South Africa
5. Department of Mathematics, University of Chakwal, Chakwal 48800, Pakistan