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 x_12 for which x_12 is not fast. For all x_12, x_12 will play squash if and only if x_12 is fast. For all x_12, x_12 is a nurse if and only if x_12 will play squash.
For all x_12, if x_12 plays squash, then x_12 is fast can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 were a nurse, then x_12 is playing squash can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 were fast, then x_12 is playing squash can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 plays squash, then x_12 is a nurse can be inferred via the universal biconditional elimination rule. There is at least one x_12 for which x_12 will not play squash can be inferred via the existential biconditional elimination rule.