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: Richard is not a doctor. For all x_2, x_2 is a scientist if and only if x_2 is a doctor.
For all x_2, if x_2 were a scientist, then x_2 is a doctor can be inferred via the universal biconditional elimination rule. For all x_2, if x_2 were a doctor, then x_2 is a scientist can be inferred via the universal biconditional elimination rule.