3D Equilibrium of 4-wheel support

[washer]

Homework Statement

The plate has a dimension of 460mm X 260mm, subjected to a central load of 400N.
Determine the reaction A and B, each representing a roller support as a wheel, located at the center of one edge. (opposite blue arrows have the same resultant value.)
Are they the same ? If not how can I find them out ?

Homework Equations

N/A

The Attempt at a Solution

I did both force and moment summation giving me A+B=200.
I am sorry if this seems like a kindergarten problem.

 

[BvU]

What did you take as rotation axes ?