[1] King Faisal Univ, Dept Basic Sci, Gen Adm Preparatory Year, POB 400, Al Hasa 31982, Saudi Arabia
[2] Abdul Wali Khan Univ, Dept Math, Mardan, Pakistan
[3] Hazara Univ, Dept Math & Stat, Mansehra, Pakistan
[4] George Mason Univ, Sch Syst Biol, Manassas, VA 22030 USA
[5] King Khalid Univ, Coll Sci, Dept Math, Abha 61413, Saudi Arabia
[6] King Faisal Univ, Coll Sci, Dept Math & Stat, POB 400, Al Hasa 31982, Saudi Arabia