SQL & PL/SQL

Dear All,

Could you please suggest what is wrong in the below statement and how can i get a output from below table. I donot want to use round( 12 *100 / (5*4)) score in subquery.

SQL> select     round( 12 *100 / (5*4)) score,                

  2            (case

  3             WHEN score between 81 and 100 then 'EXCELLENT'

  4             when score between 61 and 80  then 'GOOD'

  5             WHEN score between 41 and 60 then  'AVARAGE'

  6             else 'POOR'

  7          end) performence1

  8    from dual;

           WHEN score between 81 and 100 then 'EXCELLENT'

                *

ERROR at line 3:

ORA-29900: operator binding does not exist

ORA-06553: PLS-306: wrong number or types of arguments in call to 'SCORE'

Below query works fine

select                     
          (case
           WHEN score between 81 and 100 then 'EXCELLENT'
           when score between 61 and 80  then 'GOOD'
           WHEN score between 41 and 60 then  'AVARAGE'
           else 'POOR'
        end)
  from ( select round( 12 *100 / (5*4))score from dual );

But i want to achieve it in a single query.

Regards

Rajat