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_3, if z_3 were fast, then z_3 is running. For all z_3, z_3 is a doctor if and only if z_3 will go running. There is at least one z_3 for which if z_3 were a doctor, then z_3 is fast.
There is at least one z_3 for which if z_3 were a doctor, then z_3 is running can be inferred via the existential transitivity rule. For all z_3, if z_3 were a doctor, then z_3 is running can be inferred via the universal biconditional elimination rule. For all z_3, if z_3 goes running, then z_3 is a doctor can be inferred via the universal biconditional elimination rule.