Section 34.1-2-616 - Procedure on notice claiming excuse(a) Where the buyer receives notification of a material or indefinite delay of 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 breach of installment contracts (section 34.1-2-612), then also as to the whole:(i) Terminate and thereby discharge any unexecuted portion of the contract; or(ii) Modify the contract by agreeing to take his available quota in substitution.(b) 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.(c) The provisions of this section may not be negated by agreement except insofar as the seller has assumed a greater obligation under the preceding section.