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 Barbara sleeps, then Jessica is playing a game. If Richard were a scientist, then Barbara is sleeping. Richard is a scientist if and only if Jessica is making tea. For all x_20, if x_20 plays a game, then x_20 is making tea.
If Richard were a scientist, then Jessica is playing a game can be inferred via the transitivity rule. If Richard were a scientist, then Jessica is making tea can be inferred via the biconditional elimination rule. If Jessica makes tea, then Richard is a scientist can be inferred via the biconditional elimination rule.