[1] Vishwakarma Govt Engn Coll, Dept Math, Ahmadabad 382424, Gujarat, India
[2] Nirma Univ, Dept Math & Humanities, Ahmadabad, Gujarat, India
[3] Marwadi Univ, Dept Math, Rajkot, Gujarat, India
[4] Charotar Univ Sci & Technol CHARUSAT, PD Patel Inst Appl Sci, Dept Math Sci, Anand 388421, Gujarat, India