$\begin{aligned}
& \mathrm{B}_1=10 \log \left(\frac{\mathrm{I}}{\mathrm{I}_0}\right) \
& \mathrm{B}_2=\log \left(\frac{\mathrm{I}^{\prime}}{\mathrm{I}_0}\right)
\end{aligned}givenB_2-B_1=20\begin{aligned}
& 20=10 \log \left(\frac{\mathrm{I^{\prime}}}{\mathrm{I}}\right) \
& \mathrm{I}^{\prime}=100 \mathrm{I}
\end{aligned}$