RCW 6.44.040Determining money of the claim.(1) The money in which the parties to a transaction have agreed that payment is to be made is the proper money of the claim for payment.(2) If the parties to a transaction have not otherwise agreed, the proper money of the claim, as in each case may be appropriate, is the money:(a) Regularly used between the parties as a matter of usage or course of dealing;(b) Used at the time of a transaction in international trade, by trade usage or common practice, for valuing or settling transactions in the particular commodity or service involved; or(c) In which the loss was ultimately felt or will be incurred by the party claimant.[ 1991 c 153 s 4.]
Washington Legal Code