$.$ Suppose that the time to complete activities B$,$ C$,$ and G for the above network is

variable, but that for the remaining activities is not variable. Under the assumption

that an activity time has a beta distribution, the path duration times are independent,

the three time estimates $($in weeks$)$ are:

Activity Optimistic

time

Most likely

time

Pessimistic

time

B $2412$

C $2810$

G $258$

What is the probability that the project $($without crashing$)$ will be completed within

$18$ weeks or less?