What is the Contribution of Segments AB and CD to the Magnetic Field at Point O?

[peaceandlove]

Homework Statement

http://s619.photobucket.com/albums/tt272/babyazureyoshi/?action=view&current=014.jpg

Homework Equations

1) B_x = (µ_0 * I) / 2R at x = 0

The Attempt at a Solution

I know that segments BC and DA do not contribute to the magnetic field at O so all I need to know is the contribution for segments AB and CD. Using equation one, I simplified the formula to ((µ_0 * I) / 2) * ((1/0.6) +(1/0.4)).

 

[rl.bhat]

The relevant equation is for the circular conductor.
Ηere you have to use
B = μ_o/4π*Ι*L/R^2.
Since angle subtended by the segments at the center is π/3, you can find the lengths of the segments by using the formula L = R*θ