The surface tension of water at ${20}^0\mathrm{C} \mathrm{is} 73 \mathrm{dynes} {\mathrm{cm}}^{-1}.$ The minimum value of work done needed to increase surface area of water from $2 {\mathrm{cm}}^2 \mathrm{to} 5 {\mathrm{cm}}^2 \mathrm{is}$