The subject matter of a meeting or the determination to open or close a meeting or a portion of a meeting to public observation may be changed following public announcement under §261b.6 only if a majority of the members of the agency determines by a recorded vote that agency business so requires and that no earlier announcement of the change was possible. Public announcement of such change and the vote of each member upon such change will be made pursuant to §261b.6(c). Changes in time, including postponements and cancellations of a publicly announced meeting or portion of a meeting or changes in the place of a publicly announced meeting will be publicly announced pursuant to §261b.6(c) by the Secretary of the Board or, in the Secretary's absence, the Acting Secretary of the Board.