Some HC1 gas diffuses across a film of air 0.1 in. thick at 20C. The partial pressure

Question:

Some HC1 gas diffuses across a film of air 0.1 in. thick at 20°C. The partial pressure of HC1 on one side of the film is 0.08 atrn and it is zero on the other. Estimate the rate of diffusion, as mol HCl/s-cm2if, the total pressure is
(a) 10 atm,
(b) 1 atm,
(c) 0.1 atm. The diffusivity of HCl in air at 20°C and 1 atm is 0.145 cm2/s.