A radio station has a contest each day for a week in which the DJ randomly selects one birthday (month and day, not year) and announces it on the air. The first person with that birthday who calls the station wins a prize. A new birthday is selected for each of the 7 days, and the station doesn't mind if the same birthday is selected more than once over the course of the contest.
a. What is the list of units from which a selection will be made each day?
b. If the station did not have access to appropriate computer software or a table of random digits, explain how they could randomly choose a birthday each day.