A distance $AB$ is observed repeatedly using the same equipment and procedures, and the results, in meters, are listed:

$67\mathrm{.}401,67\mathrm{.}400,67\mathrm{.}402,67\mathrm{.}406,67\mathrm{.}401,67\mathrm{.}396,67\mathrm{.}401,67\mathrm{.}405,$ and $67\mathrm{.}404$

Calculate the line's most probable length.

Express your answer to five significant figures and include appropriate units.

Calculate the standard deviation.

Express your answer to three significant figures and include appropriate units.

Calculate the standard deviation of the mean.

Express your answer to three significant figures and include appropriate units.