$4\mathrm{.}9.$ An as$-$built survey is done to establish the floor elevations of a classroom building that will undergo renovations. The building has two main floors, multiple changes of elevation on the main floor, a mezzanine level, and a partial basement. Notes for the survey are shown below. What is the difference in elevation between

a$.$ The first and second floors at the east end of the building.

b$.$ The first and second floors at the north end of the building.

c$.$ The second floor and the mechanical room floor $($basement$).$

d$.$ The north entrance and the floor of the office suite on the northeast corner $($mezzanine level$)?$

$\backslash$table$[[$Station$,$BS$,HI,$FS$,$SS$,$Elev.,Description$],[$BM$1,4\mathrm{.}58,,,,100\mathrm{.}00,x$ on conc., $1$st floor, east entry$],[$TP$1,8\mathrm{.}25,,1\mathrm{.}59,,,],[$TP$2,8\mathrm{.}19,,1\mathrm{.}60.,,,],[1,4\mathrm{.}59,,4\mathrm{.}62,,,x$ on conc., $2$nd floor, top of east stairs$],[$TP$3,4\mathrm{.}58,,4\mathrm{.}46,,,],[2,2\mathrm{.}25,,4\mathrm{.}60,,,x$ on conc., $2$nd floor, top of north stairs$],[$TP$4,4\mathrm{.}61,,11\mathrm{.}75,,,],[$TP$5,1\mathrm{.}65,,8\mathrm{.}83,,,],[3,4\mathrm{.}58,,4\mathrm{.}58,.,,x$ on conc., $1$st floor, north entry$],[4,4\mathrm{.}58,,3\mathrm{.}91,,,x$ on conc., top of ramp in $N-S$ hallway$],[5,4\mathrm{.}64,,1\mathrm{.}91,,,x$ on conc., top of ramp in E$-$W hallway$],[6,,,,9\mathrm{.}25,,$Floor of mezzanine level$],[7,,,,5\mathrm{.}76,,$Floor of sunken area in main lobby$],[8,,,,15\mathrm{.}22,,$Floor of mechanical room, basement level$],[$BM$1,,,4\mathrm{.}64,,,]].$

Calculate HI for allstations except $6,7,$and $8$ because these are intermediate station. Calculate all station and SS elevatios.

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