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 it is late, then Karen is working. If Karen works, then it is late. If it is late, then Karen is working.
It is late if and only if Karen is working can be inferred via the biconditional introduction rule. Karen is working if and only if it is late can be inferred via the biconditional introduction rule. Karen is working if and only if it is late can be inferred via the biconditional introduction rule. It is late if and only if Karen is working can be inferred via the biconditional introduction rule.