[1] Sefako Makgatho Hlth Sci Univ, Dept Math & Appl Math, ZA-0204 Pretoria, South Africa
[2] Usmanu Danfodiyo Univ, Dept Math, Sokoto 840104, Nigeria
[3] King Fahd Univ Petr & Minerals, Interdisciplinary Res Ctr Smart Mobil & Logist, Dhahran 31261, Saudi Arabia
[4] King Fahd Univ Petr & Minerals, Dept Math, Dhahran 31261, Saudi Arabia