(a) For the evaluation of offers, the transportation officer shall give to the contracting officer, and the contracting officer shall use, the lowest available freight rates and related accessorial and incidental charges that (1) are in effect on, or become effective before, the expected date of the initial shipment and (2) are on file or published on the date of the bid opening.

(b) If rates or related charges become available after the bid opening or the due date of offers, they shall not be used in the evaluation unless they cover transportation for which no applicable rates or accessorial or incidental costs were in existence at the time of bid opening or due date of the offers.