31.3. The person responsible for engineering and acquisitions, the person responsible for administration and the person responsible for information systems are authorized to sign, for the purposes of accomplishing the mandate of the administrative unit for which they are responsible, any supply contract, auxiliary service contract or professional service contract for an amount not exceeding $25,000, any contract for the sale of movable property or for the supply of services, any contract for the sale of surplus movable property and any contract for the leasing of rolling stock.