A steady current $I$ is flowing in the $-x$ direction through each of two infinitely long wires at $y = \pm \dfrac{L}{2}$ as shown in the figure. The permeability of the medium is $\mu_{0}$. The $\overrightarrow{B}$-field at $(0,L,0)$ is
- $-\dfrac{4\mu _{0}I}{3\Pi L} \hat{Z} \\$
- $+\dfrac{4\mu _{0}I}{3\Pi L} \hat{Z} \\$
- $0 \\$
- $-\dfrac{3\mu _{0}I}{4\Pi L} \hat{Z}$