1. Department of Mathematics , King Abdulaziz University , P.O. Box 80203 , Jeddah , 21589 , Saudi Arabia
2. Department of Mathematics , Faculty of Physical Sciences, Ahmadu Bello University , Zaria , Kaduna State , Nigeria
3. Department of Mathematics , Grand Asian University , Sialkot 7KM Pasrur Road 51310 , Sialkot , Pakistan