b
Point \(P\) is situated at the mid-point of the line joining the centres of the circular wires which have same radii \((R)\). The magnetic fields \((\vec{B})\) at \(P\) due to the currents in the wires are in same direction.

Magnitude of magnetic fieldat point, \(P\)

\(B = 2\left\{ {\frac{{{\mu _0}NI{R^2}}}{{2{{\left( {{R^2} + \frac{{{R^2}}}{4}} \right)}^{3/2}}}}} \right\}\)

\(=\frac{\mu_{0} N I R^{2}}{\frac{5^{3 / 2}}{8}}=\frac{8 \mu_{0} N I}{5^{3 / 2} R}\)