How find out top 10 file with IO wait?

select * from (select b.file_name,
       a.singleblkrds,
       a.singleblkrdtim,
       a.singleblkrdtim/a.singleblkrds avg_wait
from   v$filestat a, dba_data_files b
where  a.file# = b.file_id  
and    a.singleblkrds > 0
order by avg_wait desc) where rownum < 11;