What are assigned project names?
select t1.name from projects as t1 join assignedto as t2 on t1.code = t2.project
How about names of not assigned projects?
select name from projects where code not in ( select project from assignedto )
what is the name of not assigned project with the least hours?
select name from projects where code not in ( select project from assignedto ) order by hours limit 1