(a) The effect of provisions of this chapter may be varied by agreement of the parties made at any time before or after commencement of an action, distribution, or the entry of judgment.
(b) The parties may agree upon the money to be used in a transaction giving rise to a foreign-money claim and may use different moneys for different aspects of the transaction. Stating the price in a foreign money or for a particular transaction does not require, of itself, the use of that money for other aspects of the transaction.