Square patch of length and witth somm

$=lnn$ thic.

$x=\frac{-\text{h}\text{a}\text{t}(D{)}_{BD}}{8}$

$)=(0)=(0$

a$)$ differential form of the mass tronsfor equation at st$.$ st for patch and skin side

b$)$ Fick's low and simplify.

C$)$ mass flux $n_{AP}$ if $)=(0$

d$)$ mass concontration $P_{A_{1}s},|x|=0||$

e$)$ total mass conc difference betwean the patch and the skin. Q Asp ${?}_{A,P_1\text{:}}-P_{A_{1}si}$ coefficient $D_{AP},D_{AS}$ ilpils if $P_{A1}$ is is the uniform mass cenc. Of $A$ in the skin

f$)$ thickness of the skin that all the drug is consimed.