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_3, x_3 is a scientist if and only if x_3 is a soldier. There is at least one x_3 for which if x_3 were a taxi driver, then x_3 is a soldier. For all x_3, x_3 is not a scientist.
For all x_3, if x_3 were a scientist, then x_3 is a soldier can be inferred via the universal biconditional elimination rule. For all x_3, if x_3 were a soldier, then x_3 is a scientist can be inferred via the universal biconditional elimination rule. For all x_3, x_3 is not a soldier can be inferred via the universal biconditional elimination rule.