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: It is not overcast. If David works, then it is overcast. Elisabeth is writing a letter.
David is not working can be inferred via the modus tollens rule. It is not overcast and Elisabeth is writing a letter can be inferred via the conjunction rule. Elisabeth is writing a letter and it is not overcast can be inferred via the conjunction rule.