The current in the wire is I. The current comes from infinite parallel to z-axis and finally goes to infinite parallel to y-axis as shown in the figure. Find magnetic field at O in vector form for the following current configurations.

• A

  $\frac{{\mathrm{\mu }}_0.\mathrm{I}}{2\mathrm{\pi R}}\left[\widehat{\mathrm{j}}-\frac{\left(2+7\mathrm{\pi }\right)}{4}\left(-\widehat{\mathrm{k}}\right)\right]$

• B

  $\frac{{\mathrm{\mu }}_0.\mathrm{I}}{4\mathrm{\pi R}}\left[\widehat{\mathrm{j}}+\frac{\left(2+7\mathrm{\pi }\right)}{4}\left(\widehat{\mathrm{k}}\right)\right]$

• C

  $\frac{{\mathrm{\mu }}_0.\mathrm{I}}{4\mathrm{\pi R}}\left[\widehat{\mathrm{j}}+\frac{\left(2+7\mathrm{\pi }\right)}{4}\left(-\widehat{\mathrm{k}}\right)\right]$

• D

  None of these