1. Associate Professor and Head of Mathematics Dept., American International Univ.-Bangladesh, Banani, Dhaka 1213, Bangladesh (corresponding author).
2. Professor, Engovation Research (Medical, Marine and Aerospace Mechanics), Gabriel’s Wing House, 11 Rooley Croft, Bradford, West Yorkshire BD6 1FA, U.K.
3. Dept. of Mathematical Sciences, Ball State Univ., 2000 W. University Ave., Muncie, IN 47306.