All facilities constructed by the authority shall be constructed according to plans and specifications of architects or engineers, or both, selected by the department. Such plans and specifications shall be approved by the department and by the commission. All work in the construction of facilities, or any part thereof, which is determined by the commission to be suitable and proper for construction by prison labor under force account shall be performed by such prison labor under such supervision and directions as shall be ordered by the department. All construction of facilities or any part thereof which the commission shall determine not to be suitable and proper for construction by prison labor shall be done under the supervision and direction of the commission following award for each part of the work to the lowest responsible bidder after advertising for, receipt and public opening of sealed bids. Each such invitation for bids and the bidding documents applicable thereto shall be so arranged that any alternates shall constitute cumulative deductions from the base bid rather than additions thereto. In determining the lowest bidder if funds are insufficient to construct the facility on the lowest base bid, then the commission may proceed to consider the bids upon the basis of the base bids of all bidders minus the respective reductions stated for the first alternate. If the lowest bid so determined is not then within the funds available, the commission shall proceed to consider the base bid minus the first and second alternates together to determine the lowest bid and in like manner throughout all alternates, if need be, so that in no event shall there be any discretion as to which alternate or alternates will be used in determining the lowest responsible bidder. If no bid deemed acceptable by the commission and the authority is received, all bids may be rejected, in which event bids may again from time to time be invited and acted on as provided in this section. All such contracts shall be lump sum contracts. All contracts for the entire work on a facility shall be awarded at the same time, but notice to proceed may be withheld until prior work under another contract has progressed to a point where the joint or following work can best be coordinated for the earliest completion of the entire project in a sound and workmanlike manner. Each contract shall be executed by the authority upon the determination of the commission as to the lowest bidder. Payments made by the authority under the construction contracts shall be upon the contractor's written sworn request only if endorsed as approved by the commission or in any lesser amount the commission shall endorse as having been then earned on said contract. After the contracts for a facility have been awarded, such construction cost estimate shall be revised and all extras on the contracts shall be awarded within the funds available. The authority shall pay to the commission as a part of the cost of constructing the facility such sums for the services of its employees as may be mutually agreed between the department and the commission.