Select the correct answer. Event b is dependent on event a, and event a occurs before event b. Which expression is equal to the probability of event a?
1) p(b ∩ a) / p(b)
2) p(b ∩ a) / p(b | a)
3) p(a ∩ b) / p(a | b)
4) p(a ∩ b) × p(b | a)
5) p(a ∩ b) × p(b)
