In each example, when would you use a hash and when would you use an array?

a. Counting the number of occurrences of an IP address in a log file.
b. Generating a list of users who are over disk quota for use in a report.

a. Because you will want to look up the IP addresses at random, they are best
accumulated in a hash.
b. Because they are input for a report, it is appropriate to collect the list of
users in an array.