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: It is sunny if and only if Mary is a poet. Mary is not a poet. If it is sunny, then Mary is a poet.
It is not sunny can be inferred via the modus tollens rule. If it is sunny, then Mary is a poet can be inferred via the biconditional elimination rule. If Mary were a poet, then it is sunny can be inferred via the biconditional elimination rule. It is not sunny can be inferred via the biconditional elimination rule.