wow.... i did it!!!

i assign in fixed relations:

vss = (int)(x/dxm); // to count the value of the answer as u hinted
xpt=xm[vss];        // assign xpt to xm [ array determine by vss ]

u r the best !!! thanks!

BTW i will continue to post the collaborated work here for others to learn from my comments lines in the source code xml

end of the day, would you be hosting my derived work on your forum as evidence of this good example of 21 st century collaboration cum distance learning :) ?? that will be so cool

thanks for a wonderful deep learning experience.  ;D