An outward and return walk

The graph shows a walker’s distance \(d\), in kilometres, from home after \(t\) minutes. She walks along the same straight route throughout.

1. State how long she rests.[1]
2. Calculate her speed during the first 20 minutes, in km/h.[2]
3. Calculate her average speed for the whole hour. Explain why using the final vertical coordinate as the total distance would be wrong.[3]