(1) A head to whom a request under section 7 is made may refuse to grant the request if -
(a) the record concerned does not exist or cannot be found after all reasonable steps to ascertain its whereabouts have been taken,
(b) the request does not comply with section 7(1)(b),
(c) in the opinion of the head, granting the request would, by reason of the number or nature of the records concerned or the nature of the information concerned, require the retrieval and examination of such number of records or an examination of such kind of the records concerned as to cause a substantial and unreasonable interference with or disruption of work of the public body concerned,
(d) publication of the record is required by law and is intended to be effected not later than 12 weeks after the receipt of the request by the head,
(e) the request is, in the opinion of the head, frivolous or vexatious, or forms part of a pattern of manifestly unreasonable requests from the same requester or from diff