Any help is much appreciated, having a hard time wrapping my head around probability.
Armco, a manufacturer of traffic light systems found that under accelerated life tests 95% of the newly developed systems lasted 3 years before failing to change signals properly.
a)If a city purchases 4 of these systems, what is the probability that all 4 systems would operate properly for at least 3 years?
b)Which rule of probability does this illustrate?
c)using letters to represent the four systems, write an equation to show how you arrived to the answer to part a.