An intelligence data bank center requires power 24 hours a day, 7days a week. If the main power grid fails, a backup power supply isinitiated. The backup consists of a battery driven supply inparallel with a diesel generator. The battery driven supply takesover immediately the main power grid fails. At the same time, adiesel generator is started from the battery supply. The batterydriven supply can only provide power for 60 minutes and an alarmwill sound if the charge in the battery falls below 75%. If thealarm sounds, this implies that the diesel generator has notstarted automatically and requires an operator to start itmanually.
(i) Draw the Event Tree and for the initiating event of the mainpower grid failing.