Being an introvert, I dislike public settings and try to avoid them at all cost. Up until recently, whenever I got invited to parties and events, I used to stress for days and weeks, depending on how far in advance I knew about it, on how to find an excuse so I did not have to attend. If I really had to attend, I’d play and rehearse in my head about what I’d say and what people would say and how conversations would go. That, of course, didn’t work because most of the times, these things are unpredictable.
If there is a dependency, then availability is a product of the availability of the system and dependent system. For example, if System A has 99.9% and System B has 99.9% and A depends on B, the availability of aggregate system is 99.9 * 99.9 = 99.8%