Should the Department determine that it is necessary or desirable to have a given project performed in phases, it will not be necessary to negotiate the total contract price or compensation provisions at the time the initial phase is negotiated, provided that the Department shall have determined that the firm is the best qualified to perform the whole project at a fair and reasonable cost, and the contract contains provisions that the State, at its option, may utilize the firm for other phases and that the firm will accept a fair and reasonable price for subsequent phases to be later negotiated and reflected in a subsequent written instrument. The procedure with regard to negotiation provided for in section 6106 of the Public Contract Code shall be applicable.