Algorithm for Horn formula (to determine if a Horn formula can be satis?ed) and says that the correctness of the greedy satis?ability algorithm follows from that invariant. However, it does not prove the invariant, nor does it fully explain how the invariant implies that the greedy satis?ability algorithm is correct. Write out that induction proof explicitly, and also show explicitly how the invariant implies that the greedy satis?ability algorithm is correct.