There are 42 employees in a certain college, either teaching or scientific research, or doing administrative work. In this college, professors do not perform administrative work, and young doctors under 30 are doing administrative work. Recruited from overseas, they all have a doctorate degree. Li Ming is the youngest professor in the college. He is only 29 years old. Based on the above statement, which of the following can be derived? ['Most PhDs recruited by the college from overseas are professors.', 'PhDs recruited by the college from overseas do not do administrative work.', 'The college professors are mostly overseas doctors over 30 years old.', 'Some professors in this college are not recruited from overseas.']