0 kg dog stands on a 21 kg flatboat at distance D = 6.1 m from the shore. It walks 2.8 m along the boat toward shore and then stops.

a 3.0 kg dog stands on a 21 kg flatboat at distance D = 6.1 m from the shore. It walks 2.8 m along the boat toward shore and then stops. Assuming no friction between the boat and the water, find how far the dog is then from the shore.