Universal Container's (UC) identity architect needs to recommend a license type for their new Experience...

Universal Container's (UC) identity architect needs to recommend a license type for their new Experience Cloud site that will be used by external partners (delivery providers) for reviewing and updating their accounts, downloading files provided by UC and obtaining scheduled pickup dates from their calendar.

UC is using their Salesforce production org as the identity provider for these users and the expected number of individual users is 2.5 million with 13.5 million unique logins per month.

Which of the following license types should be used to meet the requirement?