Section 2-208 of the Uniform Commercial Code provides: 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. . . [s]uch course of performance shall be relevant to show a waiver or modification of any term inconsistent with such course of performance.