Answer:
0.00893 feet elevation per 1 foot distance.
Explanation:
The hill reaches an elevation of 250 ft (above sea level) over the course of 28,000 feet. The average rate of change would be (250 ft)/(28,000 ft), or 0.00893 feet elevation/1 foot distance.
((0.00893 (feet up/foot distance))*(28,000 feet distance) = 250 feet up (elevation).