Algebra

Callie was vacationing in the Caribbean when she found a treasure map made by the famous pirate Algebeard many years before:

On the back of the map was written:

**Start halfway between the rock and the old stump. Walk so that the distance between ye and the stump is always the same as the distance between ye and the rock. When ye be exactly northwest of the waterfall, ye be standing on my buried treasure.**

Using her algebra skills, Callie was able to determine exactly where Algebeard's loot was stashed. What are the coordinates where Callie should dig?


 * Extra:** A lot of years have passed since Algebeard drew his map, and there are more stumps in the area now. Find a location for a tree stump that would make Algebeard's treasure impossible to find if it was used in the directions instead of the stump at (1,11). Explain why your location would make the directions not work.