I've gotten to this, it's still not quite right...
In other words, i'm really close but not quite there.
If the Dodo were to take the Eaglet 4 hours and drop them off with 60 km left, it would take the Eaglet 4 more hours to reach the forest. During the first 4 hours the Duck would have walked 60. So the Dodo travels back to get the duck. 2 hours the Dodo has covered 120 and the Duck has covered 30, which leaves 30 between them before they meet. So if the duck sticks put there the Dodo picks them up and gets back to 120 left to get to the forest when the Eaglet reached the forest.
In other words, i'm really close but not quite there.
Mine is in 10 ^^;; so we're both really close.