Mich. Comp. Laws § 423.274

Sec. 4. Within 10 days after a party has requested arbitration of a dispute, the department shall choose a delegate and the designated or selected exclusive collective bargaining representative of the employees, or if none, their previously designated representative in the prior mediation and fact-finding procedures, shall choose a delegate to an arbitration panel as provided in this act. The department and the employees immediately shall advise each other and the mediation board of their selections.