Find the single points of failure after a site-wide outage

Last Tuesday the head office (250 people) lost everything for 2 hours 40 minutes. A breaker on PDU-A in the comms room tripped. CORE1 has two power supplies, but both were plugged into PDU-A. The firewall and the server host running DHCP and DNS were on PDU-A too. The CIO asks for a list of every other single point of failure, ranked, with a plan that fits a fixed budget.