Help with query

Hi ,
Please help me with below sql. This sql at times causes high CPU usage and high execution times.  Below is from statspack

   CPU                  CPU per             Elapsd                     Old
  Time (s)   Executions  Exec (s)  %Total   Time (s)    Buffer Gets  Hash Value
---------- ------------ ---------- ------ ---------- --------------- ----------
    604.51           11      54.96   66.1    8672.25      30,525,577 2921280602
Module: nh@fx2.prod.erec2.weboperations.co.uk (TNS V1-V3
   select       a.application_id,       sysdate - a.completion_date as days_since_save    from       application a    where  a.applicant_id  = :applicant_id    and       a.form_ref      =
 :form_ref    and       a.finished      = 2    order by       a.completion_date desc;


SQL ordered by Elapsed time for DB: NHS  Instance: NHS1  Snaps: 39 -40