1. 1Department of Mathematics, University of Malakand at Chakdara, Dir (L), Khyber Pakhtoonkhwa, 18800, Pakistan
2. 2Faculty of Science, Department of Mathematical Sciences, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia
3. 3Department of Mathematics, Abdul Wali Khan University Mardan, Mardan, Khyber Pakhtoonkhwa, Pakistan
4. 4Department of Mathematics, University of Swat, Swat, Khyber Pakhtoonkhwa, Pakistan