Final answer:
The fire guards are expected to complete their second patrol no later than 12:00 p.m.
Step-by-step explanation:
The fire guards are expected to patrol every area of the shelter again no later than 12:00 p.m.. This means that they should complete their second patrol by midday. If they started their first patrol at 8:00 a.m., it would take them 4 hours to complete their second patrol, which would be at noon or 12:00 p.m.