Argon diffuses through a high density polyethylene (HDPE) sheet

Argon diffuses through a high density polyethylene (HDPE) sheet 40 mm thick at a rate of 4.0 A? 10–7 (cm3 STP)/cm2-s at 325 K. The pressures of argon at the two faces are 5000 kPa and 1500 kPa, which are maintained constant. Assuming conditions of steady state, what is the permeability coefficient at 325 K?