1. Department of Mathematics and Statistics, IIUI, Islamabad 44000, Pakistan
2. Department of Mathematics and Sciences, Prince Sultan University, P. O. Box 66833, Riyadh 11586, Saudi Arabia
3. Department of Medical Research, China Medical University, Taichung 40402, Taiwan
4. Department of Mathematics and Applied Mathematics, Sefako Makgatho Health Sciences University, Ga-Rankuwa 0204, South Africa