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 if and only if Charles is reading a book. Patricia is not a cashier. It is overcast if and only if Patricia is a cashier.
If it is overcast, then Charles is reading a book can be inferred via the biconditional elimination rule. If it is overcast, then Patricia is a cashier can be inferred via the biconditional elimination rule. If Charles reads a book, then it is overcast can be inferred via the biconditional elimination rule. If Patricia were a cashier, then it is overcast can be inferred via the biconditional elimination rule. It is not overcast can be inferred via the biconditional elimination rule.