(1) The head may, as respects an FOI request received by him or her (the "specified request"), extend the period specified in section 13(1) for consideration of the request by such period as he or she considers necessary but not exceeding a period of 4 weeks if, in the opinion of the head -

(a) the request relates to such number of records, or

(b) the number of other FOI requests relating either to the record or records to which the specified request relates or to information corresponding to that to which the specified request relates or to both that have been made to the FOI body concerned before the specified request was made to it and in relation to which a decision under section 13 has not been made is such,

that compliance with that subsection within the period specified therein is not reasonably possible.

(2) Where a period is extended under this section, the head concerned shall cause notice in writing or in such other form as may be determined, to be given to the requester concerned, before the expiration of the period, of the extension and the period thereof and reasons therefor.