$[25$ Pts$.]$ The normalized photoconductnce decay curve is shown below for wafer thickness of $d=0\mathrm{.}02$ and $d=0\mathrm{.}05cm.$ From these curves, determine the effective recombination lifetimes ${}_{\text{e}\text{f}\text{f}},$ the bulk lifetime ${}_B$ and the surface recombination velocity $s_r.$ It is best if you plot $\frac{1}{{}_{\text{e}\text{f}\text{f}}}$ versus $\frac{1}{d}$ and then use the equation

$\frac{1}{{}_{\text{e}\text{f}\text{f}}}=\frac{1}{{}_B}+\frac{2s_r}{d}$