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 climbs a mountain, then it is overcast. If Patricia takes a plane, then David is climbing a mountain. If it is overcast, then it is windy. If it is windy, then it is overcast. It is not windy.
It is not overcast can be inferred via the modus tollens rule. If David climbs a mountain, then it is windy can be inferred via the transitivity rule. If Patricia takes a plane, then it is overcast can be inferred via the transitivity rule. It is overcast if and only if it is windy can be inferred via the biconditional introduction rule. It is windy if and only if it is overcast can be inferred via the biconditional introduction rule.