Electric potential, infinite nonconductin sheet and particle

[jegues]

Homework Statement

See figure below,

Homework Equations

The Attempt at a Solution

I'm not sure how to use the sigma factor in this question.

I know that,

$$W= Fd$$

So,

$$W = Eqd$$

but I don't know how to get any farther.

What am I missing? How do I take advantage of sigma to get what I want?

 

[cupid.callin]

Do you know the electric field due to infinite large sheet?