Redmine

To create Time Entry with REST API this parameters should be used:
•time_entry (required): a hash of the time entry attributes, including:
◦issue_id or project_id (only one is required): the issue id or project id to log time on
◦spent_on: the date the time was spent (default to the current date)
◦hours (required): the number of spent hours
◦activity_id: the id of the time activity. This parameter is required unless a default activity is defined in Redmine.
◦comments: short description for the entry (255 characters max)

The question is where can I get list of activity_id ?