\(\phi=\frac{\mu_{0}}{2} \cdot \frac{\pi I R_{1}^{2} R_{2}^{2}}{\left(R_{1}^{2}+x^{2}\right)^{3 / 2}}\)

Putting the values,

\(\phi=\frac{4 \pi \times 10^{-7} \times \pi \times 15 \times\left(0.3 \times 10^{-2}\right)^{2} \times\left(20 \times 10^{-2}\right)^{2}}{\left[\left(0.3 \times 10^{-2}\right)^{2}+\left(15 \times 10^{-2}\right)^{2}\right]^{3 / 2}}\)

By solving, we get

\(\phi=9.116 \times 10^{-11} Wb\)