The given points (1, 2, 3, 4, 5, 6) makes 360^o angle at ‘O’. Hence angle made by vertices 1 and 2 with ‘O’ is 60^o.

Direction of magnetic field at ‘O’ due to each segment is same. Since it is symmetric star shape, magnitude will also be same.

Magnetic field due to section BC.

$\left(B_1\right)=\frac{ki}{a} \left(\sin \left(\mathrm{60°}\right)-\sin \mathrm{30°}\right)=\frac{ki}{2a} \left(\sqrt{3}-1\right)$

$B_{net}=12\times B_1=\frac{6ki}{a} \left(\sqrt{3}-1\right) \mathrm{a}\mathrm{n}\mathrm{d} \left(k=\frac{{\mu }_0}{4\pi }\right)$