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, if y were a bartender, then y is happy. There is at least one y for which if y were happy, then y is a bartender. For all y, y is a bartender if and only if y is a soldier. For all y, y is not a soldier.
There is at least one y for which y is happy if and only if y is a bartender can be inferred via the existential biconditional introduction rule. There is at least one y for which y is a bartender if and only if y is happy can be inferred via the existential biconditional introduction rule. For all y, if y were a bartender, then y is a soldier can be inferred via the universal biconditional elimination rule. For all y, if y were a soldier, then y is a bartender can be inferred via the universal biconditional elimination rule. For all y, y is not a bartender can be inferred via the universal biconditional elimination rule.