What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_12, if x_12 were happy, then x_12 is a doctor. For all x_12, if x_12 were a doctor, then x_12 is happy. James is not happy. Thomas is a musician.
James is not happy and Thomas is a musician. Thomas is a musician and James is not happy. For all x_12, x_12 is happy if and only if x_12 is a doctor. For all x_12, x_12 is a doctor if and only if x_12 is happy.