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 overcast, then Joseph is not a nurse. It is not windy. Mary is a mechanic or Joseph is a nurse. It is windy if and only if Mary is a mechanic.
If it is windy, then Mary is a mechanic can be inferred via the biconditional elimination rule. If Mary were a mechanic, then it is windy can be inferred via the biconditional elimination rule. Mary is not a mechanic can be inferred via the biconditional elimination rule.