Soluton
Explanation:
The slope of the graph between 120 minutes and 150 minutes
As the line is flat, the slope is 0. The elevation will not change because the slope is zero. You can look at the graph where a climber is climbing a mountain. The climber climbs up, then walks on the flat top. Then they slide down the mountain.
Therefore the slope of the graph between 120 and 150 minutes = 0 ,
The change in elevation is constant