Sorry there has been some error's in my previous mail, I used three sum sign, please replace the first with: ___ \ /___ a r^n not -n The second and third stays the same ___ \ /___ X*(.9)^n ___n \ /___ r^n n=0 _______________________________________________ Aquatic-Plants mailing list Aquatic-Plants at actwin_com http://www.actwin.com/mailman/listinfo/aquatic-plants