What is the magnetic field at point P in a current loop?

[luxmundi]

Homework Statement

A current is in a straight conductor of length a.
a. Show that the magnitude of the magnetic field at point P is B=√2μ₀i/8pia .
b. Use the result of part a. to find the magnetic field at point P in the current loop below
(magnitude and direction).

http://postimg.org/image/toaspcmfl/
[url=http://postimg.org/image/toaspcmfl/][img=http://s16.postimg.org/toaspcmfl/Untitled.jpg][/url]

Homework Equations

B=√2μ₀i/8pia

The Attempt at a Solution

I have part a, its just that I am having trouble going about part b, any help?

 

[metapuff]

Well, the two sections of the wire where the current points directly toward or away from P aren't going to matter, right, since i X r is zero. For the other sections, youre going to just add up the fields from each wire. You found the field for one of them in part a, and the others have similar geometries so they shouldn't be too bad. Remember that the B field goes as 1/r²!