Sections 407.900 to 407.910 shall not apply to a written contract executed prior to August 13, 1984, unless either the parties agree by mutual written consent that sections 407.900 to 407.910 shall apply or such contract is extended or renewed after August 13, 1984. The provisions of sections 407.900 to 407.910 shall prevail over any conflicting or inconsistent provisions of chapter 400 affecting the subject matter of sections 407.900 to 407.910.