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 y_4, y_4 is bored if and only if y_4 is a server. For all y_4, y_4 is bored if and only if y_4 is a sailor. There is at least one y_4 for which y_4 is not a sailor.
For all y_4, if y_4 were bored, then y_4 is a server can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were bored, then y_4 is a sailor can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were a server, then y_4 is bored can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were a sailor, then y_4 is bored can be inferred via the universal biconditional elimination rule. There is at least one y_4 for which y_4 is not bored can be inferred via the existential biconditional elimination rule.