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: John is not writing a letter. If it is overcast, then John is writing a letter. If it is not overcast, then Thomas is a nurse. Thomas is bored.
It is not overcast can be inferred via the modus tollens rule. John is not writing a letter and Thomas is bored can be inferred via the conjunction rule. Thomas is bored and John is not writing a letter can be inferred via the conjunction rule.