A distance $AB$ is observed repeatedly using the same equipment and procedures, and the results,

in meters, are listed in the following:

$120\mathrm{.}501,120\mathrm{.}503,120\mathrm{.}500,120\mathrm{.}498,120\mathrm{.}507,120\mathrm{.}502,120\mathrm{.}499,120\mathrm{.}504,120\mathrm{.}506$

$120\mathrm{.}505$

a$.$ Calculate the line's most probable length. $(2pts$

b$.$ Calculate the standard deviation. $(2pts)$

c$.$ Calculate the standard deviation of the mean for the set of results. $(2pts)$