Two concentric circular loops of radii $r_1=30 \mathrm{cm}$ and $r_2=50 \mathrm{cm}$ are placed in $X-Y$ plane as shown in the figure. A current $I=7 \mathrm{A}$ is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately

• A

  $\frac{7}{2}\hat{k} \mathrm{A} {\mathrm{m}}^2$
• Correct answer
  B

  $-\frac{7}{2}\hat{k} \mathrm{A} {\mathrm{m}}^2$
• C

  $7\hat{k} \mathrm{A} {\mathrm{m}}^2$
• D

  $-7\hat{k} \mathrm{A} {\mathrm{m}}^2$

Hence, the correct answer is option: 'B'.