SQL

I have a table a:
create tabel a( marca int4,
                       mo varchar(1)
                    );

This is the contents of the table:
marca     mo
1            C
2            C
4            B
5            O
1            C
1            B

I need a SQL interogation with following results:

marca concedii boala obligatii
  1         2           1        0
  2         1            0       0
  4         0            1       0
  5         0            0       1

How can I do that?


Thanks!