insert...

Hi,
suppose that I have two table definitions as follows:
CREATE TABLE a (first int4, second varchar(30));
CREATE TABLE b (b_first int4, b_second a, b_third bool);

How can I insert a row into table 'b'?
I tried
INSERT INTO b values (2, (1, 'something'), 't'); and
INSERT INTO b values (2, "(1, 'something')", 't');
but none of them was correct.
Then I read almost all of man pages, but unfortunately I couldn't find
anything. Maybe you can help me.
Thank you,
Lajos Kollar (kollarlajos(at)tigris(dot)klte(dot)hu)