Sudin Mandal (1), Injamam Ul Karim (2), Swapan Raha (3) (1) Department of Mathematics, Visva-Bharati, Santiniketan, West-Bengal, India-731235,, India,
(2) Department of Mathematics, Visva-Bharati, Santiniketan, West-Bengal, India-731235,, India,
(3) Visva-Bharati(, a Central University), India