6.93 Return to the context of the previous exercise and suppose that 50% of the overnight parcels are sent by means of express mail service A2 and the remaining 10% are sent by means of A3. Of those sent by means of A2, only 1% arrived late, whereas 5% of the parcels handled by A3 arrived late.

a. What is the probability that a randomly selected parcel arrived late? (Hint: A tree diagram should help.)

b. Suppose that a randomly selected overnight parcel arrived late. What is the probability that the parcel was shipped using mail service A1? That is, what is the probability of A1 given L, denoted PsA1uLd?

c. What is PsA2uLd?

d. What is PsA3uLd?