An activity on a PERT network has these time estimates: optimistic $=3,$ most likely $=5,$ and pessimistic $=12.$ What are its expected activity time and variance?

$5\mathrm{.}83$;$2\mathrm{.}25$

$5\mathrm{.}50$;$1\mathrm{.}36$

$6\mathrm{.}67$;$2\mathrm{.}25$

$5\mathrm{.}00$;$9\mathrm{.}00$

$5\mathrm{.}83$;$1\mathrm{.}50$