[1] Comsats Inst Informat Technol, Dept Math, Wancantt 47040, Pakistan
[2] Quaid I Azam Univ, Dept Math, Islamabad 44000, Pakistan
[3] King Abdulaziz Univ, Fac Sci, Dept Math, Nonlinear Anal & Appl Math NAAM Res Grp, Jeddah 21589, Saudi Arabia
[4] Comsats Inst Informat Technol, Dept Math, Sahiwal, Pakistan