1) A company has sales offices in four cities. An analysis of the company's accounts receivables reveals the number of overdue invoices by days, as shown to the right. Assume the invoices are stored and managed from a central database.

Days Overdue City A City B City C City D

Under 30 Days 120 113 216 292

30-60 Days 89 45 89 117

61 - 90 Days 24 32 62 41

Over 90 Days 20 29 44 67

a. What is the probability that a randomly selected invoice from the database is from the City C office?

b. What is the probability that a randomly selected invoice from the database is between 30 and 90 days overdue?

c. What is the probability that a randomly selected invoice from the database is over 90 days old and from the City B office?

d. If a randomly selected invoice is from the City D office, what is the probability that it is 60 or fewer days overdue?

2) The time between telephone calls to a cable television service call center follows an exponential distribution with a mean of 1.2 minutes.

a. What is the probability that the time between the next two calls will be 36 seconds or less? b. What is the probability that the time between the next two calls will be greater than 118 seconds?