Solving an Electric Field Problem: Zero Potential?

[itsrelative]

Homework Statement

The problem is as shown in the attached file.

Homework Equations

The Attempt at a Solution

I got 0 for the potential, which would mean zero for the electric field. I don't understand, in a conceptual way, how zero could be the correct answer.

 

[silvermane]

Take a peak at this thread to understand potentials and electric fields:
https://www.physicsforums.com/showthread.php?t=103794