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 David plays a game, then Sarah is a sailor. Sarah is not a sailor. If Thomas writes a letter, then Linda is playing tennis. If James cooks, then Linda is playing tennis. Thomas is writing a letter or James is cooking.
David is not playing a game can be inferred via the modus tollens rule. Linda is playing tennis can be inferred via the disjunction elimination rule.