The magnetic induction at the centre \( O \) in the figure shown is...

The magnetic induction at the centre \( O \) in the figure shown is
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(1) \( \frac{\mu_{0} \mathrm{i}}{4}\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right) \)
(2) \( \frac{\mu_{0} i}{4}\left(\frac{1}{R_{1}}+\frac{1}{R_{2}}\right) \)
(3) \( \frac{\mu_{0} \mathrm{i}}{4}\left(R_{1}-R_{2}\right) \)
(4) \( \frac{\mu_{0} i}{4}\left(R_{1}+R_{2}\right) \)