Section 2--208. Course of Performance or Practical Construction

(1)  Where  the  contract  for  sale  involves  repeated occasions for
  performance by  either  party  with  knowledge  of  the  nature  of  the
  performance and opportunity for objection to it by the other, any course
  of  performance  accepted  or  acquiesced  in without objection shall be
  relevant to determine the meaning of the agreement.
    (2) The express  terms  of  the  agreement  and  any  such  course  of
  performance,  as well as any course of dealing and usage of trade, shall
  be construed whenever reasonable as consistent with each other; but when
  such construction is unreasonable, express terms shall control course of
  performance and course of  performance  shall  control  both  course  of
  dealing and usage of trade (Section 1--205).
    (3)  Subject to the provisions of the next section on modification and
  waiver, such course of performance shall be relevant to show a waiver or
  modification of any term inconsistent with such course of performance.