1. Department of Mathematics , Quaid-I-Azam University , Islamabad 44000 , Pakistan
2. Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science , King Abdulaziz University , Jeddah 21589 , Saudi Arabia
3. Department of Mathematics , Quaid-I-Azam University 45320 , Islamabad , Pakistan , E-mail: , Tel: +92 51 90642172