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 Elisabeth were a nurse, then it is overcast. If Elisabeth were a nurse, then it is overcast. If it is overcast, then Elisabeth is a nurse.
Elisabeth is a nurse if and only if it is overcast can be inferred via the biconditional introduction rule. Elisabeth is a nurse if and only if it is overcast can be inferred via the biconditional introduction rule. It is overcast if and only if Elisabeth is a nurse can be inferred via the biconditional introduction rule. It is overcast if and only if Elisabeth is a nurse can be inferred via the biconditional introduction rule.