The hearing on the protest as provided in section 54-107 shall be open to the public, and all testimony shall be under oath administered by a certified court reporter. The city clerk, with whom such petition is filed, shall have the power to issue subpoenas to compel the attendance of witnesses and the production of documents and to receive all testimony and documentary evidence before rendering a decision as to the sufficiency of the petition. Upon failure of any witness to obey the subpoena, the city clerk may petition the municipal court for an order compelling the witness to appear and testify or produce documentary evidence. The burden of proof at the protest hearing shall be on the protestants to prove that the petition is insufficient. The result of such hearing shall be mailed to the petition representatives and protest representatives. The protest hearing shall be concluded and a decision by the city clerk rendered no later than ten days after the conclusion of the hearing. The city clerk may call upon the city attorney's office to provide legal advice during the hearing.