(1)      Tender of delivery is a condition to the buyer's duty to accept the goods and, unless otherwise agreed, to his duty to pay for them. Tender entitles the seller to acceptance of the goods and to payment according to the contract.

      (2)      Where payment is due and demanded on the delivery to the buyer of goods or documents of title, his right as against the seller to retain or dispose of them is conditional upon his making the payment due.