Adapted from problems $4\mathrm{.}8$ and $4\mathrm{.}10(40$ marks$)$

a$.$ Compute the radii $r_o$ and $r_t$ of impurity atoms

that will just fit into an FCC octahedral and

tetrahedral site, respectively.

b$.$ Using the above result, compute the radii of the

interstitial sites for FCC iron