If territory comprising an entire school district is annexed to the city and becomes a part of the first class school district, part 10 shall govern where applicable with respect to the bonded indebtedness of either district existing at the time of annexation. The first class school district board may use any funds legally available to retire the bonded indebtedness of the annexed district. If the question under section 410 is approved in the first class school district, then the chief executive officer appointed under section 420 has the powers and shall perform the duties of the board of the first class school district under this section.