1. Department of Mathematics, National Institute of Technology Manipur, Imphal 795004, India
2. Department of Mathematics, Manipur University, Imphal 795003, India
3. Department of Mathematics and Statistics, International Islamic University, Islamabad 44000, Pakistan
4. Department of Statistics and Operations Research, Faculty of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia