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: If Thomas takes a plane, then it is overcast. If it rains, then it is overcast. It is raining or Thomas is taking a plane. It is late if and only if it is overcast.
It is overcast can be inferred via the disjunction elimination rule. If it is late, then it is overcast can be inferred via the biconditional elimination rule. If it is overcast, then it is late can be inferred via the biconditional elimination rule.