1. Centre for Advanced Studies in Pure and Applied Mathematics , Bahauddin Zakariya University , Multan 60800 , Pakistan
2. Department of Basic Sciences and Humanities , Muhammad Nawaz Sharif University of Engineering and Technology , Multan 60000 , Pakistan
3. Department of Mathematics, College of Arts and Sciences , Prince Sattam bin Abdulaziz University , Wadi Aldawaser 11991 , Saudi Arabia