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_6, if x_6 were happy, then x_6 is sleeping. There is at least one x_6 for which if x_6 sleeps, then x_6 is a taxi driver. For all x_6, if x_6 were a taxi driver, then x_6 is poor. For all x_6, if x_6 were poor, then x_6 is happy.
For all x_6, if x_6 were a taxi driver, then x_6 is happy can be inferred via the universal transitivity rule. For all x_6, if x_6 were poor, then x_6 is sleeping can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 sleeps, then x_6 is poor can be inferred via the existential transitivity rule. There is at least one x_6 for which if x_6 were happy, then x_6 is a taxi driver can be inferred via the existential transitivity rule.