5. Concession contracts may not be entered into unless tenders have been called for, except:(a) where only one agent is available;
(b) where the concession contract is accessory to a leasing contract and granted to the awarder of that leasing contract;
(c) where the concession contract is of short duration, that is, for a period under 3 months, or of a non-continuous nature;
(d) where the concession contract does not grant the agent any exclusive rights;
in such cases the authorization of the board of directors of the Board is required unless it is otherwise stipulated in this Regulation.