unable to pick max value

HI
i am wirting a pl/sql block to pick a max value from the data which is combination of alpha-numeric
can u please help to find it out
 create table d(name varchar2(25),category varchar2(25));
insert into  d values('lotabcd.1',' bulk');
 insert into  d values('lotabcd.2',' bulk');
 insert into d values('lotabcd.3','bulk');
  insert into d values('lotabcd','bulk');
   insert into d values(' lotabcd.1-pk',' pk');
 insert into d values(' lotabcd.2-pk',' pk');
  insert into d values(' lotabcd.9',' bulk');
  insert into d values(' lotabcd.12','bulk');