d. Everyones zip code within a state has the same first digit. (i) x, s, z1 [State(s) LivesIn(x, s) Zip(x) = z1 ] [ y, z2 LivesIn(y, s) Zip(y) = z2 Digit(1, z1) = Digit(1, z2 )]. (ii) x, s [State(s) LivesIn(x, s) z1 Zip(x) = z1] [ y, z2 LivesIn(y, s) Zip(y) = z2 Digit(1, z1 ) = Digit(1, z2 )]. (iii) x, y, s State(s)LivesIn(x, s)LivesIn(y, s) Digit(1, Zip(x) = Zip(y)). (iv) x, y, s State(s) LivesIn(x, s) LivesIn(y, s) Digit(1, Zip(x)) = Digit(1, Zip(y))