s1 ∩ s2 = ∅, s0 ⊆ s1 ⊦ #(s0 ∩ s2) = 0, s0 ∩ s2 = ∅
Used simplifier rules: size-zero: ⊦ # s ≠ 0 → s ≠ ∅; (forward) from specification set-basic%size-zero-01: ⊦ s ≠ ∅ → # s ≠ 0; (forward) from specification set-basic