use shell balance approach to generate formula equation for solving this problem

(Directly introducing formula is unacceptable)

An open tank, 10ft in diameter, containing benzene at 25C is exposed to air. Above the liquid surface is a stagnant air film 0.2 inch thick. The specific gravity of benzene at 60F is 0.877 . The concentration of benzene outside the film is negligible. For benzene, the vapor pressure at 25C is 100 torr, and the diffusivity in air is 0.08 cm2/s.2 | P a g e If the pressure is 1atm and the air temperature is 25C, what is the loss of benzene in Ib/day