Section 2--307. Delivery in Single Lot or Several Lots.
    Unless  otherwise  agreed  all goods called for by a contract for sale
  must be tendered in a single delivery and payment is due  only  on  such
  tender  but  where the circumstances give either party the right to make
  or demand delivery in lots the price if it can  be  apportioned  may  be
  demanded for each lot.