1. Junior Research Scholar, Dept. of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
2. Senior Research Scholar, Dept. of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
3. Associate Professor, Dept. of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India (corresponding author).
4. Associate Professor, Dept. of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.