33. Solving a chemistry problem

3.19 A drop of benzene spreads over the surface of water, and after mutual saturation of the two liquids forms a lens. Explain this phenomenon. Calculate the initial and final values for the spreading coefficients of benzene in water using the given values of surface tensions (in mN/m) for various surfaces at 293 K:
Water - air 72.75
Benzene - air 28.87
Water - benzene 35.00
Water saturated with benzene - air 62.20
Benzene saturated with water - air 28.80
Estimate the value of interfacial tension at the boundary of mutually saturated solutions of water and benzene.