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 overcast or John is not happy. It is windy if and only if it is overcast. It is windy or John is happy.
If John were happy, then it is overcast can be inferred via the rewriting rule. If it is windy, then it is overcast can be inferred via the biconditional elimination rule. If it is overcast, then it is windy can be inferred via the biconditional elimination rule.