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 z_1, z_1 will sleep if and only if z_1 is a politician. For all z_1, if z_1 plays squash, then z_1 is a politician. For all z_1, z_1 will play squash or z_1 will sleep.
For all z_1, if z_1 sleeps, then z_1 is a politician can be inferred via the universal biconditional elimination rule. For all z_1, if z_1 were a politician, then z_1 is sleeping can be inferred via the universal biconditional elimination rule.