Consider the following premises. If Patricia were happy, then Barbara is not a bartender. For all x_23, x_23 is a bartender. Jessica is drinking water if and only if Patricia is not happy. Can we infer the following from them? If we can, name the inference rule being used: Jessica is drinking water.
 From the fact that for all x_23, x_23 is a bartender we can infer that Barbara is a bartender via universal instantiation. From the fact that if Patricia were happy, then Barbara is not a bartender, and that Barbara is a bartender we can infer that Patricia is not happy via modus tollens. From the fact that Jessica is drinking water if and only if Patricia is not happy we can infer that if Patricia were not happy, then Jessica is drinking water via biconditional elimination. Finally, from the fact that if Patricia were not happy, then Jessica is drinking water, and that Patricia is not happy we can infer that Jessica is drinking water via modus ponens. Therefore, the answer is yes.