Project scheduling notation in PERT/CPM Which of the following statements about standard time notations and obligations in network planning is correct?

Introduction / Context:
Pertinent exam questions on PERT/CPM test whether you recognize standard symbols and how contractual deadlines are incorporated into the network. Knowing these conventions ensures you can run forward and backward passes correctly and interpret float values.

Given Data / Assumptions:

• TE stands for earliest event occurrence time found from the forward pass.
• TL stands for latest event occurrence time found from the backward pass.
• Ts is frequently used to denote specified or contractual completion time for the project.
• At the terminal event, TL is fixed to the contractual time to seed the backward pass.

Concept / Approach:
In a forward pass, you add activity durations to find each event’s earliest occurrence time, TE. In the backward pass, you propagate constraints from the required completion time backwards to get TL values. If a contract specifies a finish time Ts, you set TL at the last event equal to Ts and compute other TL values from there.

Step-by-Step Solution:
Confirm the notation: TE = earliest occurrence time; TL = latest occurrence time; Ts = specified finish time.Recognize that the backward pass needs a finishing boundary condition: TL at the terminal event equals Ts.Therefore all four statements correctly describe standard practice.

Verification / Alternative check:
Check a simple network: fixing TL at the end to Ts ensures that float values reflect the contract, not just a theoretical schedule with no deadline.

Why Other Options Are Wrong:
Each individual statement (a–d) is true; choosing only one would ignore the rest of the correct conventions. Hence the aggregated choice is most accurate.

Common Pitfalls:
Confusing activity times with event times; forgetting to anchor the backward pass to the contractual completion time leads to incorrect floats.

Final Answer:
All the above