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: There is at least one x_5 for which if x_5 were a carpenter, then x_5 is not a taxi driver. For all x_5, x_5 is an office clerk. For all x_5, x_5 is not an office clerk.
Nothing can be inferred from these premises.