Should the Executive Officer determine that it is necessary or desirable to have a given project requiring architectural and engineering services 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 Executive Officer shall have determined that the firm is the best qualified to perform the whole project a fair and reasonable cost and that the contract contains provisions that the State, at its option, may use 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 estimates and negotiation shall otherwise be applicable.