You may need to use the appropriate technology to answer this question.

To help with preparations, a couple has devised a project network to describe the activities that must be completed by their wedding date.

i$)$

The following table lists the activity time estimates $($in weeks$)$ for each activity.

$\backslash$table$[[$Activity$,$Optimistic,Most Probable,Pessimistic$],[$A$,4,5,6],[$B$,2\mathrm{.}5,3,3\mathrm{.}5],[$C$,7,8,9],[$D$,5,5\mathrm{.}5,9],[$E$,5,7,9],[$F$,2,3,11],[$G$,7,9,15],[$H$,7,8,]]$

$($a$)$ Within $21$ weeks?

$($b$)$ Within $23$ weeks?

$($c$)$ Within $27$ weeks?