1. Department of Mathematics, University of Science and Technology, Bannu, 28100 Khyber Pakhtunkhwa, Pakistan
2. Department of Mathematics, International Islamic University, H-10, Islamabad 44000, Pakistan
3. Institute of Research and Development of Processes, University of the Basque Country, Campus of Leioa (Bizkaia), P.O. Box 644, Bilbao, Barrio Sarriena, 48940 Leioa, Spain