Please solve $(3)$ & $(4)$

Consider a leveling net as the figure. A and $B$ are two known points, the elevation of $A$ is $50\mathrm{.}00+-0\mathrm{.}00m,$ and the elevation of $B$ is $49\mathrm{.}00+-0\mathrm{.}01m.$ Observation of elevation differences are listed below.

$\backslash$table$[[$Route$,\backslash$table$[[$Elevation$],[$Difference $(m)$

Consider a leveling net as the figure. A and $B$ are two known points, the elevation of $A$ is $50\mathrm{.}00+-0\mathrm{.}00m,$ and the elevation of $B$ is $49\mathrm{.}00+-0\mathrm{.}01m.$ Observation of elevation differences are listed below.

$\backslash$table$[[$Route$,\backslash$table$[[$Elevation$],[$Difference $(m)$