PROBLEM STATEMENT The data for the normalized drug concentration change in the toenail $(\frac{C_A}{}{C}_{A,\text{m}\text{a}\text{x}})$ on the $y-$axis as a function of distance from the nail surface is shown below as a function of time.

a$)$ From this figure, estimate $($within an order of magnitude$)$ the diffusion coefficient of the drug within the toenail $).$ Note: you can make this estimate using any single curve between $2$ and $8$ hours $($though the paper said that the $25hr$ data set was anomalous$).$

b$)$ Estimate the time required for the drug to reach the bottom of the toenail if is $1000$ microns thick $(0\mathrm{.}1cm).$ Does your answer agree with the opening statement that it is hard to get a drug through a toenail by diffusion?