The Commissioner may, in writing and either generally or as otherwise provided by the instrument of delegation, delegate to a person ¾

(a) any of the powers or duties of the Commissioner under this Act, other than this power of delegation; or

(b) all or any of the powers and duties referred to in paragraph (a) for a period of not more than 30 days to enable the person to act for that period in the office of the Commissioner while the Commissioner is on leave of absence, or is unable to perform the functions of the office of Commissioner, or is absent from the State.