Okla. Stat. tit. 12A, § 12A-2-616: Procedure on Notice Claiming Excuse

(1) Where the buyer receives notification of a material or

indefinite delay or an allocation justified under the preceding

section he may by written notification to the seller as to any

delivery concerned, and where the prospective deficiency

substantially impairs the value of the whole contract under the

provisions of this article relating to breach of installment

contracts (Section 2-612), then also as to the whole,

(a) terminate and thereby discharge any unexecuted portion

of the contract; or

(b) modify the contract by agreeing to take his available

quota in substitution.

(2) If after receipt of such notification from the seller the

buyer fails so to modify the contract within a reasonable time not

exceeding thirty (30) days the contract lapses with respect to any

deliveries affected.

(3) The provisions of this section may not be negated by

agreement except in so far as the seller has assumed a greater

obligation under the preceding section.