a ∈ s, ∀ a0. ¬ a0 ∈ dom st ∩ s ⊦ # s = 0, s = ∅, (a ∈ st \ s ↔ a ∈ st) ∧ (∅)[a] = st[a]
Used simplifier rules: ⊦ ¬ a ∈ ∅; (s)