Solve this:

5. The magnetic field at the centre of circular loop in the circuit shown below is

 

$$\begin{gathered} 1) \frac{{\mu }_0}{4\mathrm{\pi }} \frac{2I}{r} \left(1 + \mathrm{\pi }\right) 2) \frac{{\mu }_0}{4\mathrm{\pi }} \frac{2I}{r} \left(\mathrm{\pi } - 1\right) \\ 3) \frac{{\mu }_0}{4\mathrm{\pi }} \frac{2I}{r} 4) \frac{{\mu }_0}{4\mathrm{\pi }} \frac{I}{r} \left(\mathrm{\pi } + 1\right) \end{gathered}$$