What is the standard deviation of a task with optimistic, most likely, and pessimistic times of $3,4,$ and $7$ days respectively assuming the estimates were made at the $90\%$ level?

Group of answer choices

$\mathrm{.}667$

$\mathrm{.}444$

$1\mathrm{.}469$

$1\mathrm{.}212$

$1\mathrm{.}538$