Final answer:
Without the specific data points from the graph showing the plane's descent, we cannot determine the exact time it took to land.
Step-by-step explanation:
To determine how long it took the plane to land, we need to interpret the graph that shows the plane's elevation in meters as a function of time in seconds. The time it takes for the plane to land corresponds to the duration from when the plane begins its descent until it reaches an elevation of 0 meters. When the elevation reaches 0, this indicates that the plane has landed. Without the specific graph data points, we cannot calculate the exact time.
However, if you need to find the slope of a line between two given points, such as one representing an elevation of 4,000 meters and another at 6,000 meters, you would calculate this by using the formula "rise over run", which is the change in the elevation (vertical axis) divided by the change in time (horizontal axis).
In the provided references where points represent altitudes or elevation, these figures seem to reflect a different scenario related to air density rather than a flight's elevation.