The life-time, t, of a bulb in a traffic signal is a random variable with density
f(t)=1 for (1<=t<=2)
where t is measure in yrs. What is the probability as a function of y that the bulb fails in less than y yrs? The traffic signal contains 3 bulbs. Assuming they fail independently, what is the probability as a function of z that none of the bulbs have to be replaced in z years?
I don't really understand what f(t) is, so I'm having problems doing this question. Would I be right to say that the last bit should be done using Poisson distribution? Help would be appreciated.