Answer
The locus is a sphere with a radius of 3 centimeters.
Work Step by Step
While this sphere is fairly hard to draw, it is not too difficult to describe. Recall, a locus the point is the same distance away from the point at all points. Since the book specifies this distance to be 3 cm, it follows that the answer is a sphere with a radius of 3 cm, for this will always be 3 centimeters away from the given point.
