A Fentanyl (pain reliever) transdermal patch is freshly applied to a patients shoulder. The patch is 2 x 2 and provides 3 mcg/cm3 at the surface of the skin. The molecular weight of Fentanyl is 336.5. Infinitely far away from the patch, the concentration of Fentanyl is zero. If the distance between the surface of the skin and the nearest blood vessel is 400 microns, determine the concentration at the blood vessel after 12 hours. Assume that the blood vessel does not affect Fentanyl concentration. The diffusion coefficient of the system is 1.5 x 10-6 cm^2/s