Girl, Boy and Dog Puzzle

The Puzzle:

Girl, Boy and Dog
A girl, a boy, and a dog are walking down a road together.

The boy walks at 5 km/h, and is just behind the girl who walks at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.

How far does the dog travel in 1 hour?
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