A lightbulb’s lifetime is exponential distribution with variance 4 years . (1) If we define X as the lifetime, find P(X>3) (Hint: you need first figure out the λ) (2) Given one lightbulb has already...

A lightbulb’s lifetime is exponential distribution with variance 4 years .

(1) If we define X as the lifetime, find P(X>3) (Hint: you need first figure out the λ)
(2) Given one lightbulb has already been lighting 2 years, what is the probability that it will continue to work at least 2 more years?

please explain fully each step