Q.One of the conditions for the activity $(i,j)$ to lie on the critical path is :

The critical-path condition for activity $(i,j)$ is $E_j-E_i=L_j-L_i=t_{ij}$. In network analysis (CPM), for each event we compute the earliest time $E$ and latest time $L$. An activity $(i,j)$ with duration $t_{ij}$ lies on the critical path when it has no float, which requires all three of these: - the events are critical: $E_i=L_i$ and $E_j=L_j$ (zero slack), and - the time available equals the activity duration: $E_j-E_i=L_j-L_i=t_{ij}$. This is exactly the condition …