What would be the best number to increase the undo tablespace and the undo_retention to do export wi

 Hi experts.
What would be the best number to increase the undo tablespace and the undo_retention to do export with consistent=y full=y ?

Oracle version 9.2.0.3
db size:

 FILE TYPE              MB
---------------- --------
DB Files Total:    71,164
Redo Log Total:     3,072
                 --------
sum                74,236



SQL> select max(bytes) from dba_segments
  2  ;

MAX(BYTES)
----------
5712642048 -------> 5.3 Gb