Winthrop Racing owns a car racing team on the East Coast. On May 25, Winthrop purchased $26,750 worth of racing tires for the cars on its team. To get the Winthrop account, the tire manufacturer offered generous terms of 5/15, net/60. The discount applies to any amount paid within the discount period. What is the unpaid balance if Winthrop paid $20,000 on June 5? (This problem involves the partial payment of an invoice within the discount period.) Round your answer to two decimal places.

$____________ unpaid balance