In 1925, a diphtheria outbreak threatened the city of Nome. The town’s supply of antitoxin had run out, and a mail shipment would have taken weeks to arrive. After learning of the crisis, 20 mushers and some 150 sled dogs, including the famous Balto, relayed fresh antitoxin 674 miles (1,085 km) in a record five and a half days, preventing an epidemic. Today, the heroic journey is commemorated by the annual Iditarod Trail Sled Dog Race. How long did a reenactment of the serum run take in 1975? Discuss