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 sleeps, then x_6 is a taxi driver. For all x_6, if x_6 sleeps, then x_6 is a taxi driver. For all x_6, if x_6 were a taxi driver, then x_6 is sleeping.
For all x_6, x_6 will sleep if and only if x_6 is a taxi driver can be inferred via the universal biconditional introduction rule. For all x_6, x_6 will sleep if and only if x_6 is a taxi driver can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is a taxi driver if and only if x_6 will sleep can be inferred via the universal biconditional introduction rule. For all x_6, x_6 is a taxi driver if and only if x_6 will sleep can be inferred via the universal biconditional introduction rule.