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_15, if x_15 plays squash, then x_15 is a carpenter. For all x_15, x_15 is not a carpenter. There is at least one x_15 for which x_15 is bored if and only if x_15 will play squash. For all x_15, x_15 will play squash if and only if x_15 is bored.
For all x_15, x_15 will not play squash can be inferred via the universal modus tollens rule. For all x_15, if x_15 plays squash, then x_15 is bored can be inferred via the universal biconditional elimination rule. There is at least one x_15 for which if x_15 were bored, then x_15 is playing squash can be inferred via the existential biconditional elimination rule. For all x_15, if x_15 were bored, then x_15 is playing squash can be inferred via the universal biconditional elimination rule. There is at least one x_15 for which if x_15 plays squash, then x_15 is bored can be inferred via the existential biconditional elimination rule.