Leon is a professor.
All professors are teachers. All researchers are professors. No teachers are students. All people who study are students. Leon is not studying or a researcher. If Leon is not studying, then Leon is a teacher.
∀x (Professor(x) → Teacher(x)) ∀x (Researcher(x) → Professor(x)) ∀x (Teacher(x) → ¬Student(x)) ∀x (Study(x) → Student(x)) ¬Study(leon) ⊕ Researcher(leon) ¬Study(leon) → Teacher(leon)