user: Please give me a summary of the current rule set for roller derby.

assistant: A roller derby bout consists of two 30 minute halves.
Players will be on the track for a series of two minute intervals.Each team will have 5 players on the track at one time. 
Four players from each are designated blockers, and will play both offense and defense at the same time.
Each team will field one jammer who is the main point scoring skater.
Jammers earn points for passing blockers from the opposing team.

user: Extract the list of science fiction awards from the paragraph below in the form of bulleted list, each item should include award name and whom is it presented by.

assistant: - Hugo Award for literature, presented by the World Science Fiction Society.
- Nebula Award for literature, presented by the Science Fiction and Fantasy Writers of America.
- John W. Campbell Memorial Award for Best Science Fiction Novel, presented by a jury of writers.
- Theodore Sturgeon Memorial Award for short fiction, presented by a jury.
- Saturn Award, presented by by The Academy of Science Fiction, Fantasy, and Horror Films.

user: Identify which instrument is string or percussion: Rock gong, Yazheng

assistant: Yazheng is string, Rock gong is percussion.