writing function but been getting this error - oracle

Question

the question:
Write a blocK PL/SQL that display the total commission amount of a job id. Use function “compute_commission” that accepts a job id equal to 9 and return his total commission of all corresponding employees.
the error:
`Error at line 11: PLS-00103: Encountered the symbol "DECLARE"
CREATE OR REPLACE FUNCTION compute_commission (C_employee_id in number)
RETURN number
is `
the code:
CREATE OR REPLACE FUNCTION compute_commission (C_employee_id in number)
RETURN number
is
sum_commission number;
begin
select sum(job_id)
into sum_commission from employees
where employee_ref_id = C_employee_id;
return sum_commission;
end compute_commission;
declare
cal_sum_commission number;
begin
cal_sum_commission = compute_commission(cal_sum_commission);
dbms_output.put_line ('employee commission is: ' || compute_commission(cal_sum_commission);
end;

Answer 1

Should be something like this:
CREATE OR REPLACE FUNCTION compute_commission (C_employee_id IN NUMBER)
RETURN NUMBER
IS
sum_commission NUMBER;
BEGIN
SELECT SUM (job_id)
INTO sum_commission
FROM employees
WHERE employee_ref_id = C_employee_id;
RETURN sum_commission;
END compute_commission;
/
DECLARE
cal_sum_commission NUMBER := 12345;
BEGIN
cal_sum_commission := compute_commission (cal_sum_commission);
DBMS_OUTPUT.put_line (
'employee commission is: ' || cal_sum_commission);
END;
/
Note that I modified anonymous PL/SQL block and
added local variable's value (otherwise you'd pass NULL to the function) (you'll, of course, use some valid value; this - 12345 - is just an example)
used local variable in DBMS_OUTPUT.PUT_LINE
terminated statement with a semi-colon (you've had a colon)
fixed assignment operator (:= instead of just =)
Also, is sum_commision really sum of JOB_ID values? Looks strange to me ...