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_6, if x_6 were fast, then x_6 is a lawyer. For all x_6, x_6 is not fast. For all x_6, if x_6 were a lawyer, then x_6 is fast. For all x_6, if x_6 were a lawyer, then x_6 is fast.
For all x_6, x_6 is not a lawyer can be inferred via the universal modus tollens rule. For all x_6, x_6 is not a lawyer can be inferred via the universal modus tollens rule. For all x_6, x_6 is fast if and only if x_6 is a lawyer can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is fast if and only if x_6 is a lawyer can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is a lawyer if and only if x_6 is fast can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is a lawyer if and only if x_6 is fast can be inferred via the universal biconditional introduction rule.