$\backslash$table$[[$Station$,$BS$,$HI$,$FS$,$Elev$],[$BM Boulder,$3\mathrm{.}21,,,],[,,,,],[$TP$1,3\mathrm{.}11,,5\mathrm{.}47,],[,,,,],[$TP$2,2\mathrm{.}19,,6\mathrm{.}83,],[,,,,],[$TP$3,6\mathrm{.}78,,2\mathrm{.}29,],[,,,,],[$TP$4,7\mathrm{.}22,,9\mathrm{.}25,],[,,,,],[$BM Poll,,,$5\mathrm{.}67,]]$

Part A $-$ Use of a single benchmark

A surveyor knows an elevation at Catch Basin to be elev$=2156\mathrm{.}77ft.$ The surveyor takes a $BS=2\mathrm{.}67ft$ on a rod at BM Catch Basin and a $FS=6\mathrm{.}72ft$ on a rod at point $x.$ What is the elevation at point $x?$

Express your answer to six significant figures.