Given the following info about a differential level loop, what is the height of instrument of the $4$th setup? $($round to the nearest mm$)$

$BM=334\mathrm{.}778m$

$BS1=8\mathrm{.}378m$ and $FS1=7\mathrm{.}916m$

$BS2=2\mathrm{.}484m$ and $FS2=0\mathrm{.}595m$

$BS3=9\mathrm{.}729m$ and $FS3=1\mathrm{.}964m$

$BS4=7\mathrm{.}120m$ and $FS4=6\mathrm{.}464m$

$BS5=1\mathrm{.}756m$ and $FS5=4\mathrm{.}686m$