Explanation:
Summary1 is based on File1 and File3. File3 has Label2 applied, and Label2 has content marking enabled, meaning the label persists in derived content. Since File3 contributes to Summary1, Summary1 inherits the sensitivity label from File3.
Summary2 is based on File2, which has Label1 applied. Label1 grants viewer permissions to authenticated users, but content marking is disabled.
Since the label still applies to the content, Summary2 inherits Label1.
Summary3 is based on File1, File2, and File3. File2 has Label1 applied, and File3 has Label2 applied, meaning the summary will inherit at least one of these labels. Since at least one labeled file is used, the summary inherits a sensitivity label.