What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: Robert is not taking a plane or it is sunny. It is cold if and only if it is late. It is not cold. Robert is taking a plane.
It is not cold and Robert is taking a plane can be inferred via the conjunction rule. Robert is taking a plane and it is not cold can be inferred via the conjunction rule. If it is cold, then it is late can be inferred via the biconditional elimination rule. If it is late, then it is cold can be inferred via the biconditional elimination rule. It is not late can be inferred via the biconditional elimination rule.