a. What work must be done to stretch a liquid of volume V with surface tension σ into a film whose thickness is ∆ ≪ 3 V ? b. Estimate how many times the work to stretch 1 g of mercury into a film whose thickness is close to the diameter of the mercury atom is less than the specific heat of vaporization of mercury, which is 290 J/g. The surface tension and density of mercury are 0.465 N/m and 13.6 g/cm³.