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: Joseph is making tea. David is not a mechanic. David is a mechanic or Richard is reading a book. If Joseph makes tea, then William is sleeping.
William is sleeping can be inferred via the modus ponens rule. Richard is reading a book can be inferred via the disjunctive syllogism rule. Joseph is making tea and David is not a mechanic can be inferred via the conjunction rule. David is not a mechanic and Joseph is making tea can be inferred via the conjunction rule.