The Central Government may, by notification in the Official Gazette, direct that subject to such conditions, if any, as may be specified in the notification--
(a) any power exercisable by the Board under this Act shall be exercisable also by [a [Principal Chief Commissioner of Customs or Chief Commissioner of Customs] or a [Principal Commissioner of Customs or Commissioner of Customs]] empowered in this behalf by the Central Government;
(b) any power exercisable by a [Principal Commissioner of Customs or Commissioner of Customs] under this Act may be exercisable also by a [Joint Commissioner of Customs] or an [Assistant Commissioner of Customs or Deputy Commissioner of Customs] empowered in this behalf by the Central Government;
(c) any power exercisable by a [Joint Commissioner of Customs] under this Act may be exercisable also by an [Assistant Commissioner of Customs or Deputy Commissioner of Customs] empowered in this behalf by the Central Government;
(d) any power exercisable by an [Assistant Commissioner of Customs or Deputy Commissioner of Customs] under this Act may be exercisable also by a Gazetted Officer of Customs empowered in this behalf by the Board.