Question

A certain company sends 40% of its overnight mail parcels via express mail service E1. Of these parcels, 2% arrive after the guaranteed delivery time (denote the event late delivery by L). Suppose that 50% of the overnight parcels are sent via express mail service E2 and the remaining 10% are sent via E3. Of those sent via E2 on 5% arrive late, whereas 1% of the parcels handled by E3 arrive late.

Part a: Draw a tree diagram for this problem.
Part b: If a record of an overnight mailing is randomly selected from the company's file, what is the probability that the parcel went via E1 and was late?
Part c: What is the probability that a randomly selected parcel arrived on time?
Part d: If a randomly selected parcel has arrived late, what is the probability that is was not sent via E2?

Answer 1