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 in the initial instance, provided that the department shall have determined that the firm is best qualified to perform the whole project at a fair and reasonable cost, and the contract contains provisions that the department, 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 estimates and negotiation shall otherwise be applicable.