If work done in increasing the size of a soap film from  $10cm\times 6cm$ to  $10cm\times 11cm$ is $2\times {10}^{-4}J,$  then the surface tension is 

• A

  $2\times {10}^{-2}N{m}^{-1}$

• B

  $2\times {10}^{-4}N{m}^{-1}$

• C

  $2\times {10}^{-6}N{m}^{-1}$

• D

  $2\times {10}^{-8}N{m}^{-1}$