School of Mathematical Sciences, Universiti of Sains Malaysia, 11800 Minden, Penang, Malaysia

**Mohd Tahir Ismail**

School of Mathematical Sciences, Universiti of Sains Malaysia, 11800 Minden, Penang, Malaysia

Samsul Ariffin Abdul Karim

Department of Fundamental and Applied Sciences, Universiti of Teknologi Petronas, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan, Malaysia