A rookie crew was left to put in the final 1 km of rail for a stretch of railroad track. When they finished, the temperature was 20oC, and they headed to town for some refreshments with their coworkers. After an hour or two, one of the old-timers noticed that the temperature had gone up to 25oC, so he said, "I hope you left some gaps to allow for expansion." By the look on their faces, he knew that they had not, and they all rushed back to the work site. The rail had buckled into an isosceles triangle. How high was the buckle?