Richard is creating a dynamic remarketing campaign on the Microsoft Audience Network and is setting the membership duration to 30 days for shopping cart abandoners. What is the minimum number of abandoners needed in this period for the remarketing to work?

For dynamic remarketing campaigns on the Microsoft Audience Network, a minimum audience size of 300 unique users is required within the specified membership duration (in this case, 30 days) for the remarketing list to be eligible for targeting. This threshold ensures sufficient data for effective ad delivery and optimization. If the list has fewer than 300 users, it will not be active for targeting. Options like 100 or 200 users are below the minimum requirement, while 1000 users is a valid but not the minimum necessary number.