the work is:
1. a contribution to a collective work;
2. a part of a motion picture or other audiovisual work;
3. a translation;
4. a supplementary work;
5. a compilation;
6. an instructional text;
7. a test;
8. answer material for a test; or
9. an atlas;
and the parties expressly agree in a written instrument signed by them that the work shall be considered a work made for hire; or by written assignment.