How to Determine E Field from Multiple Infinite Sheets?

[{taylor}]

Homework Statement

Homework Equations

E_{inf sheet}= σ/2ε0

The Attempt at a Solution

I understand that the -σ sheet will have E field lines pointing towards the sheet. But I don't understand how to add the other sheets to find the E field in a specific region.

 

[Redbelly98]

You'll need to figure out the field for each sheet, and it's direction (i.e. either towards or away from the sheet). Then it's vector addition to get the field within each region.