1. The Administrator shall communicate a copy of the request for arbitrati­on to the respondent, along with mention of the date of receipt, and shall invite him in writing to submit a short answer thereto.

2. The short answer shall also contain the preference, if any, of the respondent for the number of the arbitrators and/or for the place of arbitra­tion, if not agreed by the parties, as well as, to the extent applicable, any further particulars as to the arbitral procedure.

3. In the short answer the respondent may introduce a coun­terclaim against the claimant in accordance with the provisi­ons of article 25(2). The requi­rements mentioned in article 6(3)(c),(d) and e) apply accordingly to the counterclaim.

4. The respondent shall file the short answer with the Admi­nistrator in five copies within 14 days * after receipt of the invitation mentioned above.