The rate of change would be 200 feet per hour. We find this by subtracting the heights and dividing it by the total number of hours.
That would be 400 feet in 2 hours or just 200 feet per hour.
After 2 hours, the climber had 1,400 feet to go. If we go back 2 hours from there, we would add on another 400 feet. The peak elevation would be 1,800 feet.