What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y, if y were a sailor, then y is writing a letter. For all y, y will write a letter. There is at least one y for which y is a doctor. For all y, if y writes a letter, then y is a sailor.
For all y, y is a sailor. Some doctors will write a letter. There is at least one y for which y will write a letter and y is a doctor. For all y, y is a sailor if and only if y will write a letter. For all y, y will write a letter if and only if y is a sailor.