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, x_12 is a taxi driver if and only if x_12 will make tea. Joseph is a sailor or Elisabeth is climbing a mountain. For all x_12, x_12 is not a taxi driver. For all x_12, if x_12 were a sailor, then x_12 is making tea.
For all x_12, if x_12 were a taxi driver, then x_12 is making tea can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 makes tea, then x_12 is a taxi driver can be inferred via the universal biconditional elimination rule. For all x_12, x_12 will not make tea can be inferred via the universal biconditional elimination rule.