1. 1 Department of Mathematics , Riphah International University , Lahore , , Pakistan
2. 2 Faculty of Applied Physics and Mathematics , Gdansk University of Technology , Gdansk , Poland ; Department of Computer Science and Mathematics , Lebanese American University , Byblos , Lebanon ; Department of Physics , University of Management and Technology , Lahore , , Pakistan
3. 3 Department of Mathematics , University of Management and Technology , Lahore , Pakistan