The surface tension of a liquid is 5 N ${\mathrm{m}}^{-1}$. If a thin film formed on a loop of area 0.02 ${\mathrm{m}}^{-2}$ then its surface energy will be

• A

  $5\times {10}^{-2} \mathrm{J}$

• B

  $2.5\times {10}^{-2}\mathrm{J}$

• C

  $2\times {10}^{-1} \mathrm{J}$

• D

  $3\times {10}^{-1} \mathrm{J}$