The surface tension of soap solution is 3.5 × 10^-2 Nm^-1. The amount of work done required to increase the radius of soap bubble from 10 cm to 20 cm…

The surface tension of soap solution is $\displaystyle 3.5 \times 10^{-2} \mathrm{Nm}^{-1}$. The amount of work done required to increase the radius of soap bubble from $\displaystyle 10$ cm to $\displaystyle 20$ cm is $\displaystyle \_\_\_\_$ $\displaystyle \times 10^{-4} \mathrm{~J}$. (take $\displaystyle \pi=22 / 7$ )