MYSQL in data base management system

sir ,we are unable to execute query for function it showing error…

DELIMITER//
CREATE FUNCTION marksfunction(marks int) RETURNS varchar(50)
BEGIN
DECLARE level varchar(50);
if marks<20 THEN set level=‘Poor performance’;
ELSEIF (marks>20 and marks<60) then set level=‘Moderate performance’;
ELSEIF marks>60 then set level=‘Excellent performance’;
end IF;
RETURN(level);
END

–sir this query with same video lecture
so,sir please solve this query