For the following situations, indicate the most appropriate type of file organization. Explain your choice.

a. A local utility company has 80,000 residential and 10,000 commercial customers. The monthly billings are staggered throughout the mouth and, as a result, the cash receipts are fairly uniform throughout the month. For 99 percent of all accounts, one check per month is received. These receipts are recorded in a botch file, and the customer account records are updated biweekly. In a typical month, customer inquiries are received at the rate of about 20 per day.

b. A national credit card agency has 12 million customer accounts. On average, 30 million purchases and 700,000 receipts of payments are processed per day. Additionally, the customer support hotline provides information to approximately 150,000 credit holders and 30,000 merchants per day.

c. An airline reservations system assumes that the traveler knows the departing city. From that point, fates and flight times are examined based on the destination. When a flight is identified as being acceptable to the traveler, the availability is checked and. if necessary, a seat is reserved. The volume of transactions exceeds one-half million per day.

d. A library system stocks over 2 million books and has 30,000 patrons. Each patron is allowed to check out five books. On average, there are 1.3 copies of each title in the library. Over 3,000 books are checked out each day, with approximately the same amount being returned daily. The checked-out books are posted immediately, as well as any returns of overdue books by payments who wish to pay their fines.