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

$81\mathrm{.}401,81\mathrm{.}400,81\mathrm{.}402,81\mathrm{.}406,81\mathrm{.}401,81\mathrm{.}396,81\mathrm{.}401,81\mathrm{.}405,$ and $81\mathrm{.}404$

Part A

Determine the range within which the observations should fall $90\%$ of the time:

$$