Subject to this Act, for the purposes of this Act:
(a) a corporation may act by any person duly authorized in that behalf by the corporation;
(b) a partnership may act by any of its members or a duly authorized agent;
(c) a person of unsound mind may act by a person authorized or empowered by law to act for him or her; and
(d) any person may act by his or her agent duly authorized in that behalf.