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: Jessica is playing squash if and only if Karen is sad. For all x_14, x_14 is not sad. Barbara is listening to a song.
If Jessica plays squash, then Karen is sad can be inferred via the biconditional elimination rule. If Karen were sad, then Jessica is playing squash can be inferred via the biconditional elimination rule.