What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_4, z_4 is not an office clerk. There is at least one z_4 for which z_4 is an office clerk if and only if z_4 will write a letter. For all z_4, if z_4 were a sailor, then z_4 is an electrician. For all z_4, if z_4 were an electrician, then z_4 is writing a letter.
For all z_4, if z_4 were a sailor, then z_4 is writing a letter. There is at least one z_4 for which if z_4 were an office clerk, then z_4 is writing a letter. There is at least one z_4 for which if z_4 writes a letter, then z_4 is an office clerk. There is at least one z_4 for which z_4 will not write a letter.