1. Department of Mathematics, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711 103, India
2. Xavier Business School, St. Xavier’s University, Kolkata 700160, India
3. Department of Mathematics, Sister Nivedita University, Newtown, Kolkata 700 156, India
4. Centre for Cosmology, Astrophysics and Space Science, GLA University, Mathura 281406, Uttar Pradesh, India