Magnetic field by moving plate capacitor ?

[BREAD]

1. Homework Statement

A large parallel plate capacitor with uniform surface charge σ on
upper plate and −σ on lower is moving with a constant speed v.

Q1]Find the magnetic field between the plates and also above and below them.

Homework Equations

The Attempt at a Solution

I know that above the top capacitor, direction of B is out of the page and into the page below the top capatitor.

and as for the bottom capacitor, above : into the page , below : out of the page.

so, between the plate , same amount of B are added into the page.

but i can't understand why above and below both plates the fields cancel

 

[mfb]

but i can't understand why above and below both plates the fields cancel

They have the same magnitude (for the approximation of infinite sheets) but opposite direction.