1. Department of Mathematical Sciences, University of Lakki Marwat, Lakki Marwat 28420, Khyber Pakhtunkhwa, Pakistan
2. Department of Mathematics, University of Lahej, Lahej, Yemen
3. Department of Mathematics, University of Aden, Aden, Yemen
4. Department of Mathematics and Statistics, International Islamic University, H-10, Islamabad-44000, Pakistan