A short project is defined by activities with three time estimates $($in days$)$ as shown in the table.

$\backslash$table$[[$Activity$,$Optimistic,Most Likely,Pessimistic,Predecessor$],[$A$,4,6,8,],[$B$,5,9,13,],[$C$,10,12,15,$A$,$ B$],[$D$,9,12,16,$B$],[$E$,6,9,15,$D$],[$F$,10,13,18,$C$]]$

What is the variance of activity $E?$

a$.2\mathrm{.}25$

b$.4\mathrm{.}25$

c$.3\mathrm{.}36$

d$.5\mathrm{.}16$