Sorting in RTF template

Hi ,

We have below  BI publisher code in rtf template

<?for-each-group:current-group();./DEVICE_ID?>

<?if: xdoxslt:get_variable($_XDOCTX, 'display')=''?>

<?FIRST_NAME?>

<?TOTAL?>

<?end if?>

<?end for-each-group?>

We are seeing the output like

Name            Charge

------------------------

Now we want to sort the output based on FIRST_NAME column in ascending order.

Can you please guide me how can I achieve the same?

Thank you very much.