Magnetic susceptibility of a paramagnetic substance is

The figure shows infinitely long bent wires in the plane of paper, each carrying a current $i$ with $O$ as origin and $x$ and $y$ axes as shown. The co-ordinates of points $P \text{and} Q$ are $(2 \mathrm{m}\text{,} 0)$ and $(6 \mathrm{m}\text{,} 0)$, respectively. The magnetic induction at $P$ is given by $\frac{\alpha {\mu }_{0}i}{32\pi }$. What is the value of $\alpha$?