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: Susan is not a cashier. If David were not excited, then Linda is cooking. David is excited if and only if Susan is a cashier.
If David were excited, then Susan is a cashier can be inferred via the biconditional elimination rule. If Susan were a cashier, then David is excited can be inferred via the biconditional elimination rule. David is not excited can be inferred via the biconditional elimination rule.