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: Robert is not a lawyer. Robert is a lawyer if and only if Elisabeth is a mechanic. John is a bartender and it is windy.
John is a bartender can be inferred via the simplification rule. It is windy can be inferred via the simplification rule. If Robert were a lawyer, then Elisabeth is a mechanic can be inferred via the biconditional elimination rule. If Elisabeth were a mechanic, then Robert is a lawyer can be inferred via the biconditional elimination rule. Elisabeth is not a mechanic can be inferred via the biconditional elimination rule.