Last moment of inertia problem I have

[elsternj]

Homework Statement

Four small spheres, each of which you can regard as a point of mass 0.200kg , are arranged in a square 0.400m on a side and connected by light rods .

Find the moment of inertia of the system about an axis through the center of the square, perpendicular to its plane (an axis through point O in the figure).

Homework Equations

I = mr²

The Attempt at a Solution

Okay now where I am having trouble with this one is finding the distances of these particles from the axis of rotation. When thinking on it, It seemed that I could use components to find a vector that reaches out to the particles. (the y and x components would both be .2m and the angle at 45degrees). But in doing this, my answer wasn't right. I don't know if I am missing something mathematically here but how does one go about finding that distance?

 

[ehild]

Show the calculations in detail.

ehild