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_10, if x_10 were poor, then x_10 is a bartender. For all x_10, x_10 is a bartender or x_10 will play squash. For all x_10, if x_10 were a bartender, then x_10 is poor. There is at least one x_10 for which x_10 is poor if and only if x_10 will play squash.
For all x_10, x_10 is poor if and only if x_10 is a bartender can be inferred via the universal biconditional introduction rule. For all x_10, x_10 is a bartender if and only if x_10 is poor can be inferred via the universal biconditional introduction rule. There is at least one x_10 for which if x_10 were poor, then x_10 is playing squash can be inferred via the existential biconditional elimination rule. There is at least one x_10 for which if x_10 plays squash, then x_10 is poor can be inferred via the existential biconditional elimination rule.