Figure 1 is a graph showing how atmospheric pressure varies with height above sea level.
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Data represented in the graph:
| Height above sea level (m) | Atmospheric pressure (kPa) |
|---|---|
| 0 | 101 |
| 1000 | 90 |
| 2000 | 80 |
| 3000 | 70 |
| 4000 | 62 |
| 5000 | 54 |
| 6000 | 47 |
| 7000 | 41 |
| 8000 | 36 |
A research helicopter descends from 5000 m to 1000 m above sea level.
Use the graph to find the change in atmospheric pressure as the helicopter descends.