Okla. Stat. tit. 12A, § 12A-2-614: Substituted Performance

(1) Where without fault of either party the agreed berthing,

loading, or unloading facilities fail or an agreed type of carrier

becomes unavailable or the agreed manner of delivery otherwise

becomes commercially impracticable but a commercially reasonable

substitute is available, such substitute performance must be

tendered and accepted.

(2) If the agreed means or manner of payment fails because of

domestic or foreign governmental regulation, the seller may withhold

or stop delivery unless the buyer provides a means or manner of

payment which is commercially a substantial equivalent. If delivery

has already been taken, payment by the means or in the manner

provided by the regulation discharges the buyer's obligation unless

the regulation is discriminatory, oppressive or predatory.