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_9, x_9 is a sailor if and only if x_9 is excited. For all x_9, x_9 is excited or x_9 is not a sailor. There is at least one x_9 for which x_9 is not excited.
For all x_9, if x_9 were a sailor, then x_9 is excited can be inferred via the universal rewriting rule. For all x_9, if x_9 were a sailor, then x_9 is excited can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 were excited, then x_9 is a sailor can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which x_9 is not a sailor can be inferred via the existential biconditional elimination rule.