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 it is windy, then Charles is making tea. It is not sunny. Charles is making tea or it is not sunny. It is sunny if and only if Charles is making tea.
If it is sunny, then Charles is making tea can be inferred via the rewriting rule. If it is sunny, then Charles is making tea can be inferred via the biconditional elimination rule. If Charles makes tea, then it is sunny can be inferred via the biconditional elimination rule. Charles is not making tea can be inferred via the biconditional elimination rule.