Determine, using a barometer, the difference in elevation between $2$ points on a street where a pipe runs down, if you have the following readings: Barometric pressure at point $1$ P$1=755$mmHg$,$ barometric pressure at point $2$ P$2=728$mmHg$.$ Assume an average air density of $\backslash$rho $=1\mathrm{.}2$ Kg$/$m$3$