Plotnick (P) agreed to supply Pennsylvania (D) battery lead. Under the installment contract, numerous shipments of lead were made with P complaining that the payment for those shipments was very often late. Several shipments were not made at the times required by the contract. P then decided not to ship remaining carloads due until unless a recently delivered carload was paid for. D promised to pay 75% of the price of the prospective shipment and the full price of the third installment. P then replied that the contract was canceled unless the prior shipment was paid in full and a letter of credit was established to cover the next shipment. D then replied that he would place the overdue payment in escrow and would accept the remaining lead with a sight draft attached for the full price. Eventually, during these exchanges, the Canadian government imposed export control on lead. The trial court concluded that D did breach the contract, but it was not a material breach that excused full performance by P. P appealed.