Find The Names Of All Instructors In The Physics Department #439

{< c > | Э s (< c, a, s, y, b, r, t >ε section ∧s = “Fall” ∧ y = “2009” ∨Эu (< c, a, s, y, b, r, t >ε section ∧s = “Spring” ∧ y = “2010”

{< n, c > | Э i, a (< i, c, a, s, y > ε teaches ∧ Э d, s (< i, n, d, s > ε instructor ∧ d = “Physics”))}

{< n > | Э i, d, s (< i, n, d, s > ε instructor ∧ s > 80000)}

{< i, n, d, s > | < i, n, d, s > ε instructor ∧ s > 80000}