What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: There is at least one y for which y is a police officer if and only if y will write a letter. For all y, if y writes a letter, then y is a police officer.
There is at least one y for which if y were a police officer, then y is writing a letter can be inferred via the existential biconditional elimination rule. There is at least one y for which if y writes a letter, then y is a police officer can be inferred via the existential biconditional elimination rule.