$14.$ The estimated variance for an activity with a most likely time $($m$)$ equal to $12$ weeks, an optimistic time $($a$)$ equal to $9$ weeks, and a pessimistic time $($b$)$ equal to $18$ weeks is

a$)3\mathrm{.}75$ weeks.

b$)1\mathrm{.}50$ weeks.

c$)5\mathrm{.}25$ weeks.

d$)2\mathrm{.}25$ weeks.