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 Charles were a writer, then Karen is playing tennis. If Barbara were an electrician, then Charles is a writer. If Karen plays tennis, then Barbara is an electrician. Karen is playing tennis if and only if Susan is a musician. Susan is not a musician.
If Charles were a writer, then Barbara is an electrician can be inferred via the transitivity rule. If Barbara were an electrician, then Karen is playing tennis can be inferred via the transitivity rule. If Karen plays tennis, then Charles is a writer can be inferred via the transitivity rule. If Karen plays tennis, then Susan is a musician can be inferred via the biconditional elimination rule. If Susan were a musician, then Karen is playing tennis can be inferred via the biconditional elimination rule. Karen is not playing tennis can be inferred via the biconditional elimination rule.