Electricity and Magnetism on lines of charge

[goodam]

Homework Statement

Two infinitely-long lines of charge run parallel to the z-axis. One has a positive uniform charge per unit length, [lambda]>0, and goes through the x y plane at x=0, y=d/2. The other has a negative uniform charge per unit length, -[lambda], and goes through x=0, y=-d/2. Nothing changes with the z coordinate; the state of affairs in any plane parallel to the x y plane is the same in the x y plane.

Homework Equations

This is where I need help.

The Attempt at a Solution

My thought is the charge will be 0, but I cannot prove this without an equation or some work.

 

[dynamicsolo]

What is the question the problem is asking about?