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: If Barbara goes running, then Charles is curious. If Charles were curious, then William is rich. For all x_10, if x_10 were rich, then x_10 is writing a letter.
If Barbara goes running, then William is rich can be inferred via the transitivity rule.