Always use these options immediately after the sort command. For example

   sort -n +1 -2 costs

sorts the data in field 2 of the file costs by its arithmetic value.

   -d (Dictionary order) sort only uses
      numbers, letters and blank spaces when sorting
      the file.
   -f (Fold in lower case) sort treats all lower-case
      letters as if they were upper-case letters.
   -i (Ignore non-printing characters) sort ignores
      any characters that do not print.
   -n (Numeric order) sort recognises the value of
       numbers and sorts them in terms of their
       value.
   -r (Reverse order) sort reverses its default sort
      order.