Question

A postal sorting equipment processes mail, one at a time. The processing times, in milliseconds, of different mail are independent and uniformly distributed in [10,70]. Use the central limit theorem to approximate the probability that the number of mails processed within 3300 milliseconds is at least 75. Hint: Rewrite the event in terms of the time Y, in milliseconds, until the first 75 mails are processed.

Answer 1

value of phi(2) is from z table