Q.Draw the logic network for the following : Activities C and D both follow A, activity E follows C, activity F follows D, activity E and F precedes B.

Draw an activity-on-arrow network: $A$ first, then $C$ and $D$ from $A$'s end, $E$ after $C$ and $F$ after $D$, $E$ and $F$ merging into $B$.

This is a network-construction question from the Operations Research chapter of the TN HSC Class-11 Business Mathematics syllabus. We use the activity-on-arrow (AOA) convention and translate each precedence relation into events (circles) joined by activity arrows.

Step 1 — List the precedence relations.

• $C$ and $D$ both follow $A$.
• $E$ follows $C$.
• $F$ follows $D$.
• $E$ and $F$ both precede $B$.

Step 2 — Assign events (nodes).

• Event 1 = start.
• $A:\;1\to 2$.
• $C:\;2\to 3$ and $D:\;2\to 4$ (both burst out of event 2, the head of $A$).
• $E:\;3\to 5$ and $F:\;4\to 5$ (both merge into event 5, since both must finish before $B$).
• $B:\;5\to 6$ (end).

Step 3 — Describe the diagram. …