Within twenty (20) days after service of a demand for arbitration, the respondent or respondents shall file a response to the demand for arbitration and serve it upon the petitioner or petitioners, or their attorney. The response shall identify any defenses then known to the respondent or respondents. If a respondent fails to file a response, then the petitioner or petitioners may proceed in default to appoint an arbitration panel pursuant to § 10108 of this Chapter.