Derivation for: Fa ∧ ¬ Fc, D ∧ a = b, Rbc → c = fa / ¬ Ra(fa)
First open gap
resources: a = b, D, Fa, ¬ Fc, Ra(fa), ¬ Rbc
alias sets: a—b, c, fa
range: 1, 2, 3