The number of students crying during a 90 minute probability test is modeled by a Poisson random variable X.
(a) If p(0 < x < 3) = 18p(x = 3), find λ.
(b) Compute p(x < 5).
(c) Assuming the same ratio of student crying over the course of a 10 hour probability test, compute p(x = 4).
