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: David is a bartender if and only if Karen is a musician. Karen is not a sailor. For all x_7, x_7 is a musician if and only if x_7 is a sailor.
If David were a bartender, then Karen is a musician can be inferred via the biconditional elimination rule. If Karen were a musician, then David is a bartender can be inferred via the biconditional elimination rule. For all x_7, if x_7 were a musician, then x_7 is a sailor can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were a sailor, then x_7 is a musician can be inferred via the universal biconditional elimination rule.