A project contains activities A-J. The table below gives the immediate predecessors for each activity. The duration of each activity is assumed to follow a beta distribution. The table also indicates the most optimistic, most probable and most pessimistic duration (a, m and b) in weeks, for each activity. Expected duration (t) and corresponding variance for an activity are calculated by: (book chapter 6 in Essentials of Management Science)

t=6a+4m+bVar=(6ba)2 \begin{tabular}{lclll} \hline Activity & Immediate predecessors & a & m & b \\ \hline A & & 2 & 4 & 7 \\ B & & 3 & 5 & 7 \\ C & A & 2 & 4 & 7 \\ D & D & 1 & 3 & 4 \\ E & B, E & 3 & 5 & 7 \\ F & B, C & 2 & 2 & 2 \\ G & F & 4 & 6 & 9 \\ H & G & 3 & 4 & 5 \\ I & H, I & 3 & 4 & 6 \\ J & & 2 & 3 & 5 \\ \hline \end{tabular}