Consider the following premises. Thomas is not sad. Richard is a bartender if and only if it is overcast. If it is overcast, then Thomas is sad. Can we infer the following from them? Richard is a bartender.
 From the fact that if it is overcast, then Thomas is sad, and that Thomas is not sad we can infer that it is not overcast. Finally, from the fact that Richard is a bartender if and only if it is overcast, and that it is not overcast we can infer that Richard is not a bartender, which contradicts that Richard is a bartender. Therefore, the answer is no.