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, x will play squash if and only if x will play tennis. There is at least one x for which if x plays squash, then x is playing tennis. For all x, x will play tennis if and only if x will play squash.
For all x, if x plays squash, then x is playing tennis can be inferred via the universal biconditional elimination rule. For all x, if x plays tennis, then x is playing squash can be inferred via the universal biconditional elimination rule. For all x, if x plays tennis, then x is playing squash can be inferred via the universal biconditional elimination rule. For all x, if x plays squash, then x is playing tennis can be inferred via the universal biconditional elimination rule.