ORA-06550: line 11, column 20: PLS-00103: Encountered the symbol "<" when expecting one of the following: I got this error when i runned the block ..please help today is my exam.

```
declare
sub1 number;
sub2 number;
sub3 number;
percent real;
begin
sub1:=:Subject1;
sub2:=:Subject2;
sub3:=:Subject3;
percent:=(sub1+sub2+sub3)/3;
if (percent >=0 and <35)
then
dbms_output.put_line(F);
elsif (percent >=35 and <50)
then
dbms_output.put_line(d);
elsif (percent >=50 and <65)
then
dbms_output.put_line(c);
elsif (percent >=65 and <80)
then
dbms_output.put_line(b);
elsif  (percent >=80)
then
dbms_output.put_line(a);
endif;
end;

```