A distance AB

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

$83\mathrm{.}401,83\mathrm{.}400,83\mathrm{.}402,83\mathrm{.}406,83\mathrm{.}401,83\mathrm{.}396,83\mathrm{.}401,83\mathrm{.}405,$ and $83\mathrm{.}404$ a$.)$ Determine the range within which the observations should fall $90\%$

of the time. b$.)$Determine the range within which the observations should fall $95\%$

of the time.