trigger predicate

i have two tables.
CREATE TABLE SUPPLIER
(
AGREEMENT_ID NUMBER(8) NOT NULL,
SUPPLIER_ID NUMBER(8) NOT NULL,
LAST_UPDATE_DATE DATE,
LAST_UPDATE_PERSON_ID INTEGER
);

CREATE TABLE SUPPLIER_TRANSACTION
(
AGREEMENT_ID NUMBER(8) NOT NULL,
SUPPLIER_ID NUMBER(8) NOT NULL,
LAST_UPDATE_DATE DATE,
LAST_UPDATE_PERSON_ID INTEGER,
comments VARCHAR2(250)
);

i want to track all the records -
1)if a record insert into SUPPLIER TABLE it also insert into SUPPLIER_TRANSACTION for tracking record inserted(comments).
2)while update supplier id into SUPPLIER TABLE it also insert old value from supplier to SUPPLIER_TRANSACTION for tracking record was updated(comments).