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 nurse. There is at least one x_15 for which x_15 is a taxi driver if and only if x_15 is a soldier. For all x_15, x_15 is a soldier or x_15 is not a nurse. For all x_15, x_15 will play squash.
For all x_15, x_15 is a nurse can be inferred via the universal modus ponens rule. For all x_15, if x_15 were a nurse, then x_15 is a soldier can be inferred via the universal rewriting rule. There is at least one x_15 for which if x_15 were a taxi driver, then x_15 is a soldier can be inferred via the existential biconditional elimination rule. There is at least one x_15 for which if x_15 were a soldier, then x_15 is a taxi driver can be inferred via the existential biconditional elimination rule.