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 z for which if z were happy, then z is working. For all z, if z were happy, then z is working. For all z, if z works, then z is happy.
For all z, z is happy if and only if z will work can be inferred via the universal biconditional introduction rule. For all z, z will work if and only if z is happy can be inferred via the universal biconditional introduction rule. There is at least one z for which z is happy if and only if z will work can be inferred via the existential biconditional introduction rule. There is at least one z for which z will work if and only if z is happy can be inferred via the existential biconditional introduction rule.