Use the profile trace first to measure BA and HSC $(1/$mm$)$ for z $(\backslash$mu m$)=2\mathrm{.}4,$

$2\mathrm{.}6,2\mathrm{.}8,3\mathrm{.}0$ and then to plot BA and HSC $(1/$mm$)$ versus z $(\backslash$mu m$).$ The

measurements can be done manually using a ruler and a sharp pencil or

using digital software. It is recommended that the plots be done using

Excel and its $$smooth line$$ feature be used for interpolation between the

plotted points but this too can be done manually.