What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one x_4 for which if x_4 were a scientist, then x_4 is a nurse. For all x_4, if x_4 were a scientist, then x_4 is a nurse. For all x_4, if x_4 were a nurse, then x_4 is a scientist.
For all x_4, x_4 is a scientist if and only if x_4 is a nurse. For all x_4, x_4 is a nurse if and only if x_4 is a scientist. There is at least one x_4 for which x_4 is a scientist if and only if x_4 is a nurse. There is at least one x_4 for which x_4 is a nurse if and only if x_4 is a scientist.