What is the formula for a magnetic field due to a finite wire with current?

[meaghan]

Homework Statement

A rectangular loop with dimensions 4.20 cm by 9.50 cm carries current I. The current in the loop produces a magnetic field at the center of the loop that has magnitude 3.60×10−5T and direction away from you as you view the plane of the loop.

Homework Equations

b = mu_0 I L/ 4pi*r ,where l is (a/bsqrt(a^2+b^2)) and
(b/asqrt(a^2+b^2));
a = .042m
b = .095m

The Attempt at a Solution

i think i just put the given values into the equation, then solve for I, but I'm not sure if I'm setting it up right

 

[blue_leaf77]

First write out the general formula for a magnetic field due to a finite wire with current. The formula you write there is not correct.