Potential difference

[Avitoholis]

Ok, hear is the question I need to answer, "What is "E" in direction and magnitude at the centre of a square if q=0.1uC." Now my question is about the diagram that is provided I don't know what the values at each of the corners of the square are for, they are simply +29,-29,+9 and -9. Any ideas would be great.

[berkeman]

You need to give a more specific description of the problem, or attach a sketch of the drawing in the problem.