Section 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 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.