QUESTION $13$

Consider the following work breakdown structure:

$\backslash$table$[[$Duration Estimates $($Days$)],[$Activity$,$Precedes,Optimistic,Most Likely,Pessimistio$],[$Start$,\frac{?}{\text{b}\text{a}\text{r}}(U,V),-,-,-],[U,$W$,35,50,65],[$V$,W,x,28,40,52],[$W$,$Z$,26,35,44],[x,\frac{?}{\text{b}\text{a}\text{r}}(Y),28,40,52],[$Y$,$Z$,26,29,38],[$Z$,$End,$36,60,84],[\{$

$\backslash$table$[[$What is the estimated standard deviation in the time for activity Z$?],[3$ days$]]\}],[],[8$ days$],[5$ days$],[4$ days$],[2$ days,,,,$]]$