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, x_12 is a nurse if and only if x_12 will write a letter. Michael is writing a letter if and only if Michael is a nurse.
If Michael writes a letter, then Michael is a nurse. If Michael were a nurse, then Michael is writing a letter. For all x_12, if x_12 were a nurse, then x_12 is writing a letter. For all x_12, if x_12 writes a letter, then x_12 is a nurse.