Section 2--615. Excuse by Failure of Presupposed Conditions.

Except so far as a seller may have assumed a greater obligation and
subject to the preceding section on substituted performance:

(a) Delay in delivery or non-delivery in whole or in part by a seller
who complies with paragraphs (b) and (c) is not a breach of his duty
under a contract for sale if performance as agreed has been made
impracticable by the occurrence of a contingency the non-occurrence of
which was a basic assumption on which the contract was made or by
compliance in good faith with any applicable foreign or domestic
governmental regulation or order whether or not it later proves to be
invalid.

(b) Where the causes mentioned in paragraph (a) affect only a part of
the seller's capacity to perform, he must allocate production and
deliveries among his customers but may at his option include regular
customers not then under contract as well as his own requirements for
further manufacture. He may so allocate in any manner which is fair and
reasonable.

(c) The seller must notify the buyer seasonably that there will be
delay or non-delivery and, when allocation is required under paragraph
(b), of the estimated quota thus made available for the buyer.