Terms with respect to which the confirmatory memoranda of the parties agree or which are otherwise set forth in a writing intended by the parties as a final expression of their agreement with respect to those terms as are included in that memoranda or writing may not be contradicted by evidence of any prior agreement or of a contemporaneous oral agreement but may be explained or supplemented by any of the following:

    (a) By course of performance, course of dealing, or usage of trade under section 1303.

    (b) By evidence of consistent additional terms unless the court finds the writing to have been intended also as a complete and exclusive statement of the terms of the agreement.