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: For all x_18, x_18 is a writer. John is a soldier if and only if it is sunny. John is not a soldier.
If John were a soldier, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then John is a soldier can be inferred via the biconditional elimination rule. It is not sunny can be inferred via the biconditional elimination rule.