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: For all x_12, if x_12 cooks, then x_12 is working. John is not cooking. For all x_12, if x_12 works, then x_12 is cooking. If Robert were a lawyer, then John is working.
For all x_12, x_12 will cook if and only if x_12 will work can be inferred via the universal biconditional introduction rule. For all x_12, x_12 will work if and only if x_12 will cook can be inferred via the universal biconditional introduction rule.