The patch for delivering the drug through the skin has a thickness of 2 mm and A 0.06 M drug solution is contained in a capsule with a diameter of 3 cm. paste this A 250 m thick polymer membrane was placed between the capsule and the skin before put The diffusion coefficient of the drug in solution is 5.4 x 10-6 cm2 /sec, and in the polymer - 3 - The diffusion coefficient of is 1.8 x 10-7 cm2 /sec. The equilibrium concentration in the polymer phase is 0.6 times the equilibrium concentration in solution. It is assumed that the drug is rapidly absorbed into the skin and the concentration at the polymer-skin interface is zero. (a) How much of the drug in the capsule is absorbed during the first 2 hours? (b) When does the excretion rate of the drug become half of the initial rate? How many moles have been released so far? (c) Can you suggest a way to achieve a nearly constant rate of excretion of the drug?