Section 2--311. Options and Cooperation Respecting Performance

(1)  An  agreement  for  sale which is otherwise sufficiently definite
  (subsection (3) of Section 2--204) to be a contract is not made  invalid
  by the fact that it leaves particulars of performance to be specified by
  one  of  the  parties. Any such specification must be made in good faith
  and within limits set by commercial reasonableness.
    (2) Unless otherwise agreed specifications relating to  assortment  of
  the  goods are at the buyer's option and except as otherwise provided in
  subsections  (1)  (c)  and  (3)  of  Section  2--319  specifications  or
  arrangements relating to shipment are at the seller's option.
    (3) Where such specification would materially affect the other party's
  performance  but is not seasonably made or where one party's cooperation
  is necessary  to  the  agreed  performance  of  the  other  but  is  not
  seasonably  forthcoming,  the  other  party  in  addition  to  all other
  remedies
         (a) is excused for any resulting delay in  his  own  performance;
             and
         (b) may  also  either proceed to perform in any reasonable manner
             or after the time for a material part of his own  performance
             treat  the  failure to specify or to cooperate as a breach by
             failure to deliver or accept the goods.