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